lodash.compat.js 162 KB

Edit Raw Blame History

/**
 * @license
 * Lo-Dash 1.0.2 (Custom Build) <http://lodash.com/>
 * Build: `lodash -o ./dist/lodash.compat.js`
 * Copyright 2012-2013 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.4.4 <http://underscorejs.org/>
 * Copyright 2009-2013 Jeremy Ashkenas, DocumentCloud Inc.
 * Available under MIT license <http://lodash.com/license>
 */
;(function(window, undefined) {

  /** Detect free variable `exports` */
  var freeExports = typeof exports == 'object' && exports;

  /** Detect free variable `module` */
  var freeModule = typeof module == 'object' && module && module.exports == freeExports && module;

  /** Detect free variable `global` and use it as `window` */
  var freeGlobal = typeof global == 'object' && global;
  if (freeGlobal.global === freeGlobal) {
    window = freeGlobal;
  }

  /** Used for array and object method references */
  var arrayRef = [],
      objectRef = {};

  /** Used to generate unique IDs */
  var idCounter = 0;

  /** Used internally to indicate various things */
  var indicatorObject = objectRef;

  /** Used by `cachedContains` as the default size when optimizations are enabled for large arrays */
  var largeArraySize = 30;

  /** Used to restore the original `_` reference in `noConflict` */
  var oldDash = window._;

  /** Used to match HTML entities */
  var reEscapedHtml = /&(?:amp|lt|gt|quot|#39);/g;

  /** Used to match empty string literals in compiled template source */
  var reEmptyStringLeading = /\b__p \+= '';/g,
      reEmptyStringMiddle = /\b(__p \+=) '' \+/g,
      reEmptyStringTrailing = /(__e\(.*?\)|\b__t\)) \+\n'';/g;

  /** Used to match regexp flags from their coerced string values */
  var reFlags = /\w*$/;

  /** Used to detect if a method is native */
  var reNative = RegExp('^' +
    (objectRef.valueOf + '')
      .replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
      .replace(/valueOf|for [^\]]+/g, '.+?') + '$'
  );

  /**
   * Used to match ES6 template delimiters
   * http://people.mozilla.org/~jorendorff/es6-draft.html#sec-7.8.6
   */
  var reEsTemplate = /\$\{([^\\}]*(?:\\.[^\\}]*)*)\}/g;

  /** Used to match "interpolate" template delimiters */
  var reInterpolate = /<%=([\s\S]+?)%>/g;

  /** Used to ensure capturing order of template delimiters */
  var reNoMatch = /($^)/;

  /** Used to match HTML characters */
  var reUnescapedHtml = /[&<>"']/g;

  /** Used to match unescaped characters in compiled string literals */
  var reUnescapedString = /['\n\r\t\u2028\u2029\\]/g;

  /** Used to fix the JScript [[DontEnum]] bug */
  var shadowed = [
    'constructor', 'hasOwnProperty', 'isPrototypeOf', 'propertyIsEnumerable',
    'toLocaleString', 'toString', 'valueOf'
  ];

  /** Used to make template sourceURLs easier to identify */
  var templateCounter = 0;

  /** Native method shortcuts */
  var ceil = Math.ceil,
      concat = arrayRef.concat,
      floor = Math.floor,
      getPrototypeOf = reNative.test(getPrototypeOf = Object.getPrototypeOf) && getPrototypeOf,
      hasOwnProperty = objectRef.hasOwnProperty,
      push = arrayRef.push,
      toString = objectRef.toString;

  /* Native method shortcuts for methods with the same name as other `lodash` methods */
  var nativeBind = reNative.test(nativeBind = slice.bind) && nativeBind,
      nativeIsArray = reNative.test(nativeIsArray = Array.isArray) && nativeIsArray,
      nativeIsFinite = window.isFinite,
      nativeIsNaN = window.isNaN,
      nativeKeys = reNative.test(nativeKeys = Object.keys) && nativeKeys,
      nativeMax = Math.max,
      nativeMin = Math.min,
      nativeRandom = Math.random;

  /** `Object#toString` result shortcuts */
  var argsClass = '[object Arguments]',
      arrayClass = '[object Array]',
      boolClass = '[object Boolean]',
      dateClass = '[object Date]',
      funcClass = '[object Function]',
      numberClass = '[object Number]',
      objectClass = '[object Object]',
      regexpClass = '[object RegExp]',
      stringClass = '[object String]';

  /** Detect various environments */
  var isIeOpera = !!window.attachEvent,
      isV8 = nativeBind && !/\n|true/.test(nativeBind + isIeOpera);

  /* Detect if `Function#bind` exists and is inferred to be fast (all but V8) */
  var isBindFast = nativeBind && !isV8;

  /* Detect if `Object.keys` exists and is inferred to be fast (IE, Opera, V8) */
  var isKeysFast = nativeKeys && (isIeOpera || isV8);

  /**
   * Detect the JScript [[DontEnum]] bug:
   *
   * In IE < 9 an objects own properties, shadowing non-enumerable ones, are
   * made non-enumerable as well.
   */
  var hasDontEnumBug;

  /**
   * Detect if a `prototype` properties are enumerable by default:
   *
   * Firefox < 3.6, Opera > 9.50 - Opera < 11.60, and Safari < 5.1
   * (if the prototype or a property on the prototype has been set)
   * incorrectly sets a function's `prototype` property [[Enumerable]]
   * value to `true`.
   */
  var hasEnumPrototype;

  /** Detect if own properties are iterated after inherited properties (IE < 9) */
  var iteratesOwnLast;

  /**
   * Detect if `Array#shift` and `Array#splice` augment array-like objects
   * incorrectly:
   *
   * Firefox < 10, IE compatibility mode, and IE < 9 have buggy Array `shift()`
   * and `splice()` functions that fail to remove the last element, `value[0]`,
   * of array-like objects even though the `length` property is set to `0`.
   * The `shift()` method is buggy in IE 8 compatibility mode, while `splice()`
   * is buggy regardless of mode in IE < 9 and buggy in compatibility mode in IE 9.
   */
  var hasObjectSpliceBug = (hasObjectSpliceBug = { '0': 1, 'length': 1 },
    arrayRef.splice.call(hasObjectSpliceBug, 0, 1), hasObjectSpliceBug[0]);

  /** Detect if `arguments` object indexes are non-enumerable (Firefox < 4, IE < 9, PhantomJS, Safari < 5.1) */
  var nonEnumArgs = true;

  (function() {
    var props = [];
    function ctor() { this.x = 1; }
    ctor.prototype = { 'valueOf': 1, 'y': 1 };
    for (var prop in new ctor) { props.push(prop); }
    for (prop in arguments) { nonEnumArgs = !prop; }

    hasDontEnumBug = !/valueOf/.test(props);
    hasEnumPrototype = ctor.propertyIsEnumerable('prototype');
    iteratesOwnLast = props[0] != 'x';
  }(1));

  /** Detect if `arguments` objects are `Object` objects (all but Opera < 10.5) */
  var argsAreObjects = arguments.constructor == Object;

  /** Detect if `arguments` objects [[Class]] is unresolvable (Firefox < 4, IE < 9) */
  var noArgsClass = !isArguments(arguments);

  /**
   * Detect lack of support for accessing string characters by index:
   *
   * IE < 8 can't access characters by index and IE 8 can only access
   * characters by index on string literals.
   */
  var noCharByIndex = ('x'[0] + Object('x')[0]) != 'xx';

  /**
   * Detect if a DOM node's [[Class]] is unresolvable (IE < 9)
   * and that the JS engine won't error when attempting to coerce an object to
   * a string without a `toString` function.
   */
  try {
    var noNodeClass = toString.call(document) == objectClass && !({ 'toString': 0 } + '');
  } catch(e) { }

  /** Used to identify object classifications that `_.clone` supports */
  var cloneableClasses = {};
  cloneableClasses[funcClass] = false;
  cloneableClasses[argsClass] = cloneableClasses[arrayClass] =
  cloneableClasses[boolClass] = cloneableClasses[dateClass] =
  cloneableClasses[numberClass] = cloneableClasses[objectClass] =
  cloneableClasses[regexpClass] = cloneableClasses[stringClass] = true;

  /** Used to lookup a built-in constructor by [[Class]] */
  var ctorByClass = {};
  ctorByClass[arrayClass] = Array;
  ctorByClass[boolClass] = Boolean;
  ctorByClass[dateClass] = Date;
  ctorByClass[objectClass] = Object;
  ctorByClass[numberClass] = Number;
  ctorByClass[regexpClass] = RegExp;
  ctorByClass[stringClass] = String;

  /** Used to determine if values are of the language type Object */
  var objectTypes = {
    'boolean': false,
    'function': true,
    'object': true,
    'number': false,
    'string': false,
    'undefined': false
  };

  /** Used to escape characters for inclusion in compiled string literals */
  var stringEscapes = {
    '\\': '\\',
    "'": "'",
    '\n': 'n',
    '\r': 'r',
    '\t': 't',
    '\u2028': 'u2028',
    '\u2029': 'u2029'
  };

  /*--------------------------------------------------------------------------*/

  /**
   * Creates a `lodash` object, that wraps the given `value`, to enable method
   * chaining.
   *
   * In addition to Lo-Dash methods, wrappers also have the following `Array` methods:
   * `concat`, `join`, `pop`, `push`, `reverse`, `shift`, `slice`, `sort`, `splice`,
   * and `unshift`
   *
   * The chainable wrapper functions are:
   * `after`, `assign`, `bind`, `bindAll`, `bindKey`, `chain`, `compact`, `compose`,
   * `concat`, `countBy`, `debounce`, `defaults`, `defer`, `delay`, `difference`,
   * `filter`, `flatten`, `forEach`, `forIn`, `forOwn`, `functions`, `groupBy`,
   * `initial`, `intersection`, `invert`, `invoke`, `keys`, `map`, `max`, `memoize`,
   * `merge`, `min`, `object`, `omit`, `once`, `pairs`, `partial`, `partialRight`,
   * `pick`, `pluck`, `push`, `range`, `reject`, `rest`, `reverse`, `shuffle`,
   * `slice`, `sort`, `sortBy`, `splice`, `tap`, `throttle`, `times`, `toArray`,
   * `union`, `uniq`, `unshift`, `values`, `where`, `without`, `wrap`, and `zip`
   *
   * The non-chainable wrapper functions are:
   * `clone`, `cloneDeep`, `contains`, `escape`, `every`, `find`, `has`, `identity`,
   * `indexOf`, `isArguments`, `isArray`, `isBoolean`, `isDate`, `isElement`, `isEmpty`,
   * `isEqual`, `isFinite`, `isFunction`, `isNaN`, `isNull`, `isNumber`, `isObject`,
   * `isPlainObject`, `isRegExp`, `isString`, `isUndefined`, `join`, `lastIndexOf`,
   * `mixin`, `noConflict`, `pop`, `random`, `reduce`, `reduceRight`, `result`,
   * `shift`, `size`, `some`, `sortedIndex`, `template`, `unescape`, and `uniqueId`
   *
   * The wrapper functions `first` and `last` return wrapped values when `n` is
   * passed, otherwise they return unwrapped values.
   *
   * @name _
   * @constructor
   * @category Chaining
   * @param {Mixed} value The value to wrap in a `lodash` instance.
   * @returns {Object} Returns a `lodash` instance.
   */
  function lodash(value) {
    // exit early if already wrapped, even if wrapped by a different `lodash` constructor
    if (value && typeof value == 'object' && value.__wrapped__) {
      return value;
    }
    // allow invoking `lodash` without the `new` operator
    if (!(this instanceof lodash)) {
      return new lodash(value);
    }
    this.__wrapped__ = value;
  }

  /**
   * By default, the template delimiters used by Lo-Dash are similar to those in
   * embedded Ruby (ERB). Change the following template settings to use alternative
   * delimiters.
   *
   * @static
   * @memberOf _
   * @type Object
   */
  lodash.templateSettings = {

    /**
     * Used to detect `data` property values to be HTML-escaped.
     *
     * @memberOf _.templateSettings
     * @type RegExp
     */
    'escape': /<%-([\s\S]+?)%>/g,

    /**
     * Used to detect code to be evaluated.
     *
     * @memberOf _.templateSettings
     * @type RegExp
     */
    'evaluate': /<%([\s\S]+?)%>/g,

    /**
     * Used to detect `data` property values to inject.
     *
     * @memberOf _.templateSettings
     * @type RegExp
     */
    'interpolate': reInterpolate,

    /**
     * Used to reference the data object in the template text.
     *
     * @memberOf _.templateSettings
     * @type String
     */
    'variable': '',

    /**
     * Used to import variables into the compiled template.
     *
     * @memberOf _.templateSettings
     * @type Object
     */
    'imports': {

      /**
       * A reference to the `lodash` function.
       *
       * @memberOf _.templateSettings.imports
       * @type Function
       */
      '_': lodash
    }
  };

  /*--------------------------------------------------------------------------*/

  /**
   * The template used to create iterator functions.
   *
   * @private
   * @param {Obect} data The data object used to populate the text.
   * @returns {String} Returns the interpolated text.
   */
  var iteratorTemplate = function(obj) {

    var __p = 'var index, iterable = ' +
    (obj.firstArg ) +
    ', result = iterable;\nif (!iterable) return result;\n' +
    (obj.top ) +
    ';\n';
     if (obj.arrays) {
    __p += 'var length = iterable.length; index = -1;\nif (' +
    (obj.arrays ) +
    ') {  ';
     if (obj.noCharByIndex) {
    __p += '\n  if (isString(iterable)) {\n    iterable = iterable.split(\'\')\n  }  ';
     } ;
    __p += '\n  while (++index < length) {\n    ' +
    (obj.loop ) +
    '\n  }\n}\nelse {  ';
      } else if (obj.nonEnumArgs) {
    __p += '\n  var length = iterable.length; index = -1;\n  if (length && isArguments(iterable)) {\n    while (++index < length) {\n      index += \'\';\n      ' +
    (obj.loop ) +
    '\n    }\n  } else {  ';
     } ;

     if (obj.hasEnumPrototype) {
    __p += '\n  var skipProto = typeof iterable == \'function\';\n  ';
     } ;

     if (obj.isKeysFast && obj.useHas) {
    __p += '\n  var ownIndex = -1,\n      ownProps = objectTypes[typeof iterable] ? nativeKeys(iterable) : [],\n      length = ownProps.length;\n\n  while (++ownIndex < length) {\n    index = ownProps[ownIndex];\n    ';
     if (obj.hasEnumPrototype) {
    __p += 'if (!(skipProto && index == \'prototype\')) {\n  ';
     } ;
    __p +=
    (obj.loop ) +
    '';
     if (obj.hasEnumPrototype) {
    __p += '}\n';
     } ;
    __p += '  }  ';
     } else {
    __p += '\n  for (index in iterable) {';
        if (obj.hasEnumPrototype || obj.useHas) {
    __p += '\n    if (';
          if (obj.hasEnumPrototype) {
    __p += '!(skipProto && index == \'prototype\')';
     }      if (obj.hasEnumPrototype && obj.useHas) {
    __p += ' && ';
     }      if (obj.useHas) {
    __p += 'hasOwnProperty.call(iterable, index)';
     }    ;
    __p += ') {    ';
     } ;
    __p +=
    (obj.loop ) +
    ';    ';
     if (obj.hasEnumPrototype || obj.useHas) {
    __p += '\n    }';
     } ;
    __p += '\n  }  ';
     } ;

     if (obj.hasDontEnumBug) {
    __p += '\n\n  var ctor = iterable.constructor;\n    ';
     for (var k = 0; k < 7; k++) {
    __p += '\n  index = \'' +
    (obj.shadowed[k] ) +
    '\';\n  if (';
          if (obj.shadowed[k] == 'constructor') {
    __p += '!(ctor && ctor.prototype === iterable) && ';
          } ;
    __p += 'hasOwnProperty.call(iterable, index)) {\n    ' +
    (obj.loop ) +
    '\n  }    ';
     } ;

     } ;

     if (obj.arrays || obj.nonEnumArgs) {
    __p += '\n}';
     } ;
    __p +=
    (obj.bottom ) +
    ';\nreturn result';


    return __p
  };

  /** Reusable iterator options for `assign` and `defaults` */
  var defaultsIteratorOptions = {
    'args': 'object, source, guard',
    'top':
      'var args = arguments,\n' +
      '    argsIndex = 0,\n' +
      "    argsLength = typeof guard == 'number' ? 2 : args.length;\n" +
      'while (++argsIndex < argsLength) {\n' +
      '  iterable = args[argsIndex];\n' +
      '  if (iterable && objectTypes[typeof iterable]) {',
    'loop': "if (typeof result[index] == 'undefined') result[index] = iterable[index]",
    'bottom': '  }\n}'
  };

  /** Reusable iterator options shared by `each`, `forIn`, and `forOwn` */
  var eachIteratorOptions = {
    'args': 'collection, callback, thisArg',
    'top': "callback = callback && typeof thisArg == 'undefined' ? callback : createCallback(callback, thisArg)",
    'arrays': "typeof length == 'number'",
    'loop': 'if (callback(iterable[index], index, collection) === false) return result'
  };

  /** Reusable iterator options for `forIn` and `forOwn` */
  var forOwnIteratorOptions = {
    'top': 'if (!objectTypes[typeof iterable]) return result;\n' + eachIteratorOptions.top,
    'arrays': false
  };

  /*--------------------------------------------------------------------------*/

  /**
   * Creates a function optimized to search large arrays for a given `value`,
   * starting at `fromIndex`, using strict equality for comparisons, i.e. `===`.
   *
   * @private
   * @param {Array} array The array to search.
   * @param {Mixed} value The value to search for.
   * @param {Number} [fromIndex=0] The index to search from.
   * @param {Number} [largeSize=30] The length at which an array is considered large.
   * @returns {Boolean} Returns `true`, if `value` is found, else `false`.
   */
  function cachedContains(array, fromIndex, largeSize) {
    fromIndex || (fromIndex = 0);

    var length = array.length,
        isLarge = (length - fromIndex) >= (largeSize || largeArraySize);

    if (isLarge) {
      var cache = {},
          index = fromIndex - 1;

      while (++index < length) {
        // manually coerce `value` to a string because `hasOwnProperty`, in some
        // older versions of Firefox, coerces objects incorrectly
        var key = array[index] + '';
        (hasOwnProperty.call(cache, key) ? cache[key] : (cache[key] = [])).push(array[index]);
      }
    }
    return function(value) {
      if (isLarge) {
        var key = value + '';
        return hasOwnProperty.call(cache, key) && indexOf(cache[key], value) > -1;
      }
      return indexOf(array, value, fromIndex) > -1;
    }
  }

  /**
   * Used by `_.max` and `_.min` as the default `callback` when a given
   * `collection` is a string value.
   *
   * @private
   * @param {String} value The character to inspect.
   * @returns {Number} Returns the code unit of given character.
   */
  function charAtCallback(value) {
    return value.charCodeAt(0);
  }

  /**
   * Used by `sortBy` to compare transformed `collection` values, stable sorting
   * them in ascending order.
   *
   * @private
   * @param {Object} a The object to compare to `b`.
   * @param {Object} b The object to compare to `a`.
   * @returns {Number} Returns the sort order indicator of `1` or `-1`.
   */
  function compareAscending(a, b) {
    var ai = a.index,
        bi = b.index;

    a = a.criteria;
    b = b.criteria;

    // ensure a stable sort in V8 and other engines
    // http://code.google.com/p/v8/issues/detail?id=90
    if (a !== b) {
      if (a > b || typeof a == 'undefined') {
        return 1;
      }
      if (a < b || typeof b == 'undefined') {
        return -1;
      }
    }
    return ai < bi ? -1 : 1;
  }

  /**
   * Creates a function that, when called, invokes `func` with the `this` binding
   * of `thisArg` and prepends any `partialArgs` to the arguments passed to the
   * bound function.
   *
   * @private
   * @param {Function|String} func The function to bind or the method name.
   * @param {Mixed} [thisArg] The `this` binding of `func`.
   * @param {Array} partialArgs An array of arguments to be partially applied.
   * @param {Object} [rightIndicator] Used to indicate partially applying arguments from the right.
   * @returns {Function} Returns the new bound function.
   */
  function createBound(func, thisArg, partialArgs, rightIndicator) {
    var isFunc = isFunction(func),
        isPartial = !partialArgs,
        key = thisArg;

    // juggle arguments
    if (isPartial) {
      partialArgs = thisArg;
    }
    if (!isFunc) {
      thisArg = func;
    }

    function bound() {
      // `Function#bind` spec
      // http://es5.github.com/#x15.3.4.5
      var args = arguments,
          thisBinding = isPartial ? this : thisArg;

      if (!isFunc) {
        func = thisArg[key];
      }
      if (partialArgs.length) {
        args = args.length
          ? (args = slice(args), rightIndicator ? args.concat(partialArgs) : partialArgs.concat(args))
          : partialArgs;
      }
      if (this instanceof bound) {
        // ensure `new bound` is an instance of `bound` and `func`
        noop.prototype = func.prototype;
        thisBinding = new noop;
        noop.prototype = null;

        // mimic the constructor's `return` behavior
        // http://es5.github.com/#x13.2.2
        var result = func.apply(thisBinding, args);
        return isObject(result) ? result : thisBinding;
      }
      return func.apply(thisBinding, args);
    }
    return bound;
  }

  /**
   * Produces a callback bound to an optional `thisArg`. If `func` is a property
   * name, the created callback will return the property value for a given element.
   * If `func` is an object, the created callback will return `true` for elements
   * that contain the equivalent object properties, otherwise it will return `false`.
   *
   * @private
   * @param {Mixed} [func=identity] The value to convert to a callback.
   * @param {Mixed} [thisArg] The `this` binding of the created callback.
   * @param {Number} [argCount=3] The number of arguments the callback accepts.
   * @returns {Function} Returns a callback function.
   */
  function createCallback(func, thisArg, argCount) {
    if (func == null) {
      return identity;
    }
    var type = typeof func;
    if (type != 'function') {
      if (type != 'object') {
        return function(object) {
          return object[func];
        };
      }
      var props = keys(func);
      return function(object) {
        var length = props.length,
            result = false;
        while (length--) {
          if (!(result = isEqual(object[props[length]], func[props[length]], indicatorObject))) {
            break;
          }
        }
        return result;
      };
    }
    if (typeof thisArg != 'undefined') {
      if (argCount === 1) {
        return function(value) {
          return func.call(thisArg, value);
        };
      }
      if (argCount === 2) {
        return function(a, b) {
          return func.call(thisArg, a, b);
        };
      }
      if (argCount === 4) {
        return function(accumulator, value, index, object) {
          return func.call(thisArg, accumulator, value, index, object);
        };
      }
      return function(value, index, object) {
        return func.call(thisArg, value, index, object);
      };
    }
    return func;
  }

  /**
   * Creates compiled iteration functions.
   *
   * @private
   * @param {Object} [options1, options2, ...] The compile options object(s).
   *  arrays - A string of code to determine if the iterable is an array or array-like.
   *  useHas - A boolean to specify using `hasOwnProperty` checks in the object loop.
   *  args - A string of comma separated arguments the iteration function will accept.
   *  top - A string of code to execute before the iteration branches.
   *  loop - A string of code to execute in the object loop.
   *  bottom - A string of code to execute after the iteration branches.
   *
   * @returns {Function} Returns the compiled function.
   */
  function createIterator() {
    var data = {
      // support properties
      'hasDontEnumBug': hasDontEnumBug,
      'hasEnumPrototype': hasEnumPrototype,
      'isKeysFast': isKeysFast,
      'nonEnumArgs': nonEnumArgs,
      'noCharByIndex': noCharByIndex,
      'shadowed': shadowed,

      // iterator options
      'arrays': 'isArray(iterable)',
      'bottom': '',
      'loop': '',
      'top': '',
      'useHas': true
    };

    // merge options into a template data object
    for (var object, index = 0; object = arguments[index]; index++) {
      for (var key in object) {
        data[key] = object[key];
      }
    }
    var args = data.args;
    data.firstArg = /^[^,]+/.exec(args)[0];

    // create the function factory
    var factory = Function(
        'createCallback, hasOwnProperty, isArguments, isArray, isString, ' +
        'objectTypes, nativeKeys',
      'return function(' + args + ') {\n' + iteratorTemplate(data) + '\n}'
    );
    // return the compiled function
    return factory(
      createCallback, hasOwnProperty, isArguments, isArray, isString,
      objectTypes, nativeKeys
    );
  }

  /**
   * A function compiled to iterate `arguments` objects, arrays, objects, and
   * strings consistenly across environments, executing the `callback` for each
   * element in the `collection`. The `callback` is bound to `thisArg` and invoked
   * with three arguments; (value, index|key, collection). Callbacks may exit
   * iteration early by explicitly returning `false`.
   *
   * @private
   * @type Function
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array|Object|String} Returns `collection`.
   */
  var each = createIterator(eachIteratorOptions);

  /**
   * Used by `template` to escape characters for inclusion in compiled
   * string literals.
   *
   * @private
   * @param {String} match The matched character to escape.
   * @returns {String} Returns the escaped character.
   */
  function escapeStringChar(match) {
    return '\\' + stringEscapes[match];
  }

  /**
   * Used by `escape` to convert characters to HTML entities.
   *
   * @private
   * @param {String} match The matched character to escape.
   * @returns {String} Returns the escaped character.
   */
  function escapeHtmlChar(match) {
    return htmlEscapes[match];
  }

  /**
   * Checks if `value` is a DOM node in IE < 9.
   *
   * @private
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true` if the `value` is a DOM node, else `false`.
   */
  function isNode(value) {
    // IE < 9 presents DOM nodes as `Object` objects except they have `toString`
    // methods that are `typeof` "string" and still can coerce nodes to strings
    return typeof value.toString != 'function' && typeof (value + '') == 'string';
  }

  /**
   * A no-operation function.
   *
   * @private
   */
  function noop() {
    // no operation performed
  }

  /**
   * Slices the `collection` from the `start` index up to, but not including,
   * the `end` index.
   *
   * Note: This function is used, instead of `Array#slice`, to support node lists
   * in IE < 9 and to ensure dense arrays are returned.
   *
   * @private
   * @param {Array|Object|String} collection The collection to slice.
   * @param {Number} start The start index.
   * @param {Number} end The end index.
   * @returns {Array} Returns the new array.
   */
  function slice(array, start, end) {
    start || (start = 0);
    if (typeof end == 'undefined') {
      end = array ? array.length : 0;
    }
    var index = -1,
        length = end - start || 0,
        result = Array(length < 0 ? 0 : length);

    while (++index < length) {
      result[index] = array[start + index];
    }
    return result;
  }

  /**
   * Used by `unescape` to convert HTML entities to characters.
   *
   * @private
   * @param {String} match The matched character to unescape.
   * @returns {String} Returns the unescaped character.
   */
  function unescapeHtmlChar(match) {
    return htmlUnescapes[match];
  }

  /*--------------------------------------------------------------------------*/

  /**
   * Checks if `value` is an `arguments` object.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is an `arguments` object, else `false`.
   * @example
   *
   * (function() { return _.isArguments(arguments); })(1, 2, 3);
   * // => true
   *
   * _.isArguments([1, 2, 3]);
   * // => false
   */
  function isArguments(value) {
    return toString.call(value) == argsClass;
  }
  // fallback for browsers that can't detect `arguments` objects by [[Class]]
  if (noArgsClass) {
    isArguments = function(value) {
      return value ? hasOwnProperty.call(value, 'callee') : false;
    };
  }

  /**
   * Iterates over `object`'s own and inherited enumerable properties, executing
   * the `callback` for each property. The `callback` is bound to `thisArg` and
   * invoked with three arguments; (value, key, object). Callbacks may exit iteration
   * early by explicitly returning `false`.
   *
   * @static
   * @memberOf _
   * @type Function
   * @category Objects
   * @param {Object} object The object to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns `object`.
   * @example
   *
   * function Dog(name) {
   *   this.name = name;
   * }
   *
   * Dog.prototype.bark = function() {
   *   alert('Woof, woof!');
   * };
   *
   * _.forIn(new Dog('Dagny'), function(value, key) {
   *   alert(key);
   * });
   * // => alerts 'name' and 'bark' (order is not guaranteed)
   */
  var forIn = createIterator(eachIteratorOptions, forOwnIteratorOptions, {
    'useHas': false
  });

  /**
   * Iterates over an object's own enumerable properties, executing the `callback`
   * for each property. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, key, object). Callbacks may exit iteration early by explicitly
   * returning `false`.
   *
   * @static
   * @memberOf _
   * @type Function
   * @category Objects
   * @param {Object} object The object to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns `object`.
   * @example
   *
   * _.forOwn({ '0': 'zero', '1': 'one', 'length': 2 }, function(num, key) {
   *   alert(key);
   * });
   * // => alerts '0', '1', and 'length' (order is not guaranteed)
   */
  var forOwn = createIterator(eachIteratorOptions, forOwnIteratorOptions);

  /**
   * Checks if `value` is an array.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is an array, else `false`.
   * @example
   *
   * (function() { return _.isArray(arguments); })();
   * // => false
   *
   * _.isArray([1, 2, 3]);
   * // => true
   */
  var isArray = nativeIsArray || function(value) {
    // `instanceof` may cause a memory leak in IE 7 if `value` is a host object
    // http://ajaxian.com/archives/working-aroung-the-instanceof-memory-leak
    return (argsAreObjects && value instanceof Array) || toString.call(value) == arrayClass;
  };

  /**
   * Creates an array composed of the own enumerable property names of `object`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The object to inspect.
   * @returns {Array} Returns a new array of property names.
   * @example
   *
   * _.keys({ 'one': 1, 'two': 2, 'three': 3 });
   * // => ['one', 'two', 'three'] (order is not guaranteed)
   */
  var keys = !nativeKeys ? shimKeys : function(object) {
    if (!isObject(object)) {
      return [];
    }
    if ((hasEnumPrototype && typeof object == 'function') ||
        (nonEnumArgs && object.length && isArguments(object))) {
      return shimKeys(object);
    }
    return nativeKeys(object);
  };

  /**
   * A fallback implementation of `isPlainObject` that checks if a given `value`
   * is an object created by the `Object` constructor, assuming objects created
   * by the `Object` constructor have no inherited enumerable properties and that
   * there are no `Object.prototype` extensions.
   *
   * @private
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if `value` is a plain object, else `false`.
   */
  function shimIsPlainObject(value) {
    // avoid non-objects and false positives for `arguments` objects
    var result = false;
    if (!(value && typeof value == 'object') || isArguments(value)) {
      return result;
    }
    // check that the constructor is `Object` (i.e. `Object instanceof Object`)
    var ctor = value.constructor;
    if ((!isFunction(ctor) && (!noNodeClass || !isNode(value))) || ctor instanceof ctor) {
      // IE < 9 iterates inherited properties before own properties. If the first
      // iterated property is an object's own property then there are no inherited
      // enumerable properties.
      if (iteratesOwnLast) {
        forIn(value, function(value, key, object) {
          result = !hasOwnProperty.call(object, key);
          return false;
        });
        return result === false;
      }
      // In most environments an object's own properties are iterated before
      // its inherited properties. If the last iterated property is an object's
      // own property then there are no inherited enumerable properties.
      forIn(value, function(value, key) {
        result = key;
      });
      return result === false || hasOwnProperty.call(value, result);
    }
    return result;
  }

  /**
   * A fallback implementation of `Object.keys` that produces an array of the
   * given object's own enumerable property names.
   *
   * @private
   * @param {Object} object The object to inspect.
   * @returns {Array} Returns a new array of property names.
   */
  function shimKeys(object) {
    var result = [];
    forOwn(object, function(value, key) {
      result.push(key);
    });
    return result;
  }

  /**
   * Used to convert characters to HTML entities:
   *
   * Though the `>` character is escaped for symmetry, characters like `>` and `/`
   * don't require escaping in HTML and have no special meaning unless they're part
   * of a tag or an unquoted attribute value.
   * http://mathiasbynens.be/notes/ambiguous-ampersands (under "semi-related fun fact")
   */
  var htmlEscapes = {
    '&': '&amp;',
    '<': '&lt;',
    '>': '&gt;',
    '"': '&quot;',
    "'": '&#39;'
  };

  /** Used to convert HTML entities to characters */
  var htmlUnescapes = invert(htmlEscapes);

  /*--------------------------------------------------------------------------*/

  /**
   * Assigns own enumerable properties of source object(s) to the destination
   * object. Subsequent sources will overwrite propery assignments of previous
   * sources. If a `callback` function is passed, it will be executed to produce
   * the assigned values. The `callback` is bound to `thisArg` and invoked with
   * two arguments; (objectValue, sourceValue).
   *
   * @static
   * @memberOf _
   * @type Function
   * @alias extend
   * @category Objects
   * @param {Object} object The destination object.
   * @param {Object} [source1, source2, ...] The source objects.
   * @param {Function} [callback] The function to customize assigning values.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns the destination object.
   * @example
   *
   * _.assign({ 'name': 'moe' }, { 'age': 40 });
   * // => { 'name': 'moe', 'age': 40 }
   *
   * var defaults = _.partialRight(_.assign, function(a, b) {
   *   return typeof a == 'undefined' ? b : a;
   * });
   *
   * var food = { 'name': 'apple' };
   * defaults(food, { 'name': 'banana', 'type': 'fruit' });
   * // => { 'name': 'apple', 'type': 'fruit' }
   */
  var assign = createIterator(defaultsIteratorOptions, {
    'top':
      defaultsIteratorOptions.top.replace(';',
        ';\n' +
        "if (argsLength > 3 && typeof args[argsLength - 2] == 'function') {\n" +
        '  var callback = createCallback(args[--argsLength - 1], args[argsLength--], 2);\n' +
        "} else if (argsLength > 2 && typeof args[argsLength - 1] == 'function') {\n" +
        '  callback = args[--argsLength];\n' +
        '}'
      ),
    'loop': 'result[index] = callback ? callback(result[index], iterable[index]) : iterable[index]'
  });

  /**
   * Creates a clone of `value`. If `deep` is `true`, nested objects will also
   * be cloned, otherwise they will be assigned by reference. If a `callback`
   * function is passed, it will be executed to produce the cloned values. If
   * `callback` returns `undefined`, cloning will be handled by the method instead.
   * The `callback` is bound to `thisArg` and invoked with one argument; (value).
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to clone.
   * @param {Boolean} [deep=false] A flag to indicate a deep clone.
   * @param {Function} [callback] The function to customize cloning values.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @param- {Array} [stackA=[]] Internally used to track traversed source objects.
   * @param- {Array} [stackB=[]] Internally used to associate clones with source counterparts.
   * @returns {Mixed} Returns the cloned `value`.
   * @example
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * var shallow = _.clone(stooges);
   * shallow[0] === stooges[0];
   * // => true
   *
   * var deep = _.clone(stooges, true);
   * deep[0] === stooges[0];
   * // => false
   *
   * _.mixin({
   *   'clone': _.partialRight(_.clone, function(value) {
   *     return _.isElement(value) ? value.cloneNode(false) : undefined;
   *   })
   * });
   *
   * var clone = _.clone(document.body);
   * clone.childNodes.length;
   * // => 0
   */
  function clone(value, deep, callback, thisArg, stackA, stackB) {
    var result = value;

    // allows working with "Collections" methods without using their `callback`
    // argument, `index|key`, for this method's `callback`
    if (typeof deep == 'function') {
      thisArg = callback;
      callback = deep;
      deep = false;
    }
    if (typeof callback == 'function') {
      callback = typeof thisArg == 'undefined' ? callback : createCallback(callback, thisArg, 1);
      result = callback(result);

      var done = typeof result != 'undefined';
      if (!done) {
        result = value;
      }
    }
    // inspect [[Class]]
    var isObj = isObject(result);
    if (isObj) {
      var className = toString.call(result);
      if (!cloneableClasses[className] || (noNodeClass && isNode(result))) {
        return result;
      }
      var isArr = isArray(result);
    }
    // shallow clone
    if (!isObj || !deep) {
      return isObj && !done
        ? (isArr ? slice(result) : assign({}, result))
        : result;
    }
    var ctor = ctorByClass[className];
    switch (className) {
      case boolClass:
      case dateClass:
        return done ? result : new ctor(+result);

      case numberClass:
      case stringClass:
        return done ? result : new ctor(result);

      case regexpClass:
        return done ? result : ctor(result.source, reFlags.exec(result));
    }
    // check for circular references and return corresponding clone
    stackA || (stackA = []);
    stackB || (stackB = []);

    var length = stackA.length;
    while (length--) {
      if (stackA[length] == value) {
        return stackB[length];
      }
    }
    // init cloned object
    if (!done) {
      result = isArr ? ctor(result.length) : {};

      // add array properties assigned by `RegExp#exec`
      if (isArr) {
        if (hasOwnProperty.call(value, 'index')) {
          result.index = value.index;
        }
        if (hasOwnProperty.call(value, 'input')) {
          result.input = value.input;
        }
      }
    }
    // add the source value to the stack of traversed objects
    // and associate it with its clone
    stackA.push(value);
    stackB.push(result);

    // recursively populate clone (susceptible to call stack limits)
    (isArr ? forEach : forOwn)(done ? result : value, function(objValue, key) {
      result[key] = clone(objValue, deep, callback, undefined, stackA, stackB);
    });

    return result;
  }

  /**
   * Creates a deep clone of `value`. If a `callback` function is passed, it will
   * be executed to produce the cloned values. If `callback` returns the value it
   * was passed, cloning will be handled by the method instead. The `callback` is
   * bound to `thisArg` and invoked with one argument; (value).
   *
   * Note: This function is loosely based on the structured clone algorithm. Functions
   * and DOM nodes are **not** cloned. The enumerable properties of `arguments` objects and
   * objects created by constructors other than `Object` are cloned to plain `Object` objects.
   * See http://www.w3.org/TR/html5/infrastructure.html#internal-structured-cloning-algorithm.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to deep clone.
   * @param {Function} [callback] The function to customize cloning values.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the deep cloned `value`.
   * @example
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * var deep = _.cloneDeep(stooges);
   * deep[0] === stooges[0];
   * // => false
   *
   * var view = {
   *   'label': 'docs',
   *   'node': element
   * };
   *
   * var clone = _.cloneDeep(view, function(value) {
   *   return _.isElement(value) ? value.cloneNode(true) : value;
   * });
   *
   * clone.node == view.node;
   * // => false
   */
  function cloneDeep(value, callback, thisArg) {
    return clone(value, true, callback, thisArg);
  }

  /**
   * Assigns own enumerable properties of source object(s) to the destination
   * object for all destination properties that resolve to `undefined`. Once a
   * property is set, additional defaults of the same property will be ignored.
   *
   * @static
   * @memberOf _
   * @type Function
   * @category Objects
   * @param {Object} object The destination object.
   * @param {Object} [source1, source2, ...] The source objects.
   * @param- {Object} [guard] Internally used to allow working with `_.reduce`
   *  without using its callback's `key` and `object` arguments as sources.
   * @returns {Object} Returns the destination object.
   * @example
   *
   * var food = { 'name': 'apple' };
   * _.defaults(food, { 'name': 'banana', 'type': 'fruit' });
   * // => { 'name': 'apple', 'type': 'fruit' }
   */
  var defaults = createIterator(defaultsIteratorOptions);

  /**
   * Creates a sorted array of all enumerable properties, own and inherited,
   * of `object` that have function values.
   *
   * @static
   * @memberOf _
   * @alias methods
   * @category Objects
   * @param {Object} object The object to inspect.
   * @returns {Array} Returns a new array of property names that have function values.
   * @example
   *
   * _.functions(_);
   * // => ['all', 'any', 'bind', 'bindAll', 'clone', 'compact', 'compose', ...]
   */
  function functions(object) {
    var result = [];
    forIn(object, function(value, key) {
      if (isFunction(value)) {
        result.push(key);
      }
    });
    return result.sort();
  }

  /**
   * Checks if the specified object `property` exists and is a direct property,
   * instead of an inherited property.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The object to check.
   * @param {String} property The property to check for.
   * @returns {Boolean} Returns `true` if key is a direct property, else `false`.
   * @example
   *
   * _.has({ 'a': 1, 'b': 2, 'c': 3 }, 'b');
   * // => true
   */
  function has(object, property) {
    return object ? hasOwnProperty.call(object, property) : false;
  }

  /**
   * Creates an object composed of the inverted keys and values of the given `object`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The object to invert.
   * @returns {Object} Returns the created inverted object.
   * @example
   *
   *  _.invert({ 'first': 'moe', 'second': 'larry' });
   * // => { 'moe': 'first', 'larry': 'second' } (order is not guaranteed)
   */
  function invert(object) {
    var index = -1,
        props = keys(object),
        length = props.length,
        result = {};

    while (++index < length) {
      var key = props[index];
      result[object[key]] = key;
    }
    return result;
  }

  /**
   * Checks if `value` is a boolean value.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a boolean value, else `false`.
   * @example
   *
   * _.isBoolean(null);
   * // => false
   */
  function isBoolean(value) {
    return value === true || value === false || toString.call(value) == boolClass;
  }

  /**
   * Checks if `value` is a date.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a date, else `false`.
   * @example
   *
   * _.isDate(new Date);
   * // => true
   */
  function isDate(value) {
    return value instanceof Date || toString.call(value) == dateClass;
  }

  /**
   * Checks if `value` is a DOM element.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a DOM element, else `false`.
   * @example
   *
   * _.isElement(document.body);
   * // => true
   */
  function isElement(value) {
    return value ? value.nodeType === 1 : false;
  }

  /**
   * Checks if `value` is empty. Arrays, strings, or `arguments` objects with a
   * length of `0` and objects with no own enumerable properties are considered
   * "empty".
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Array|Object|String} value The value to inspect.
   * @returns {Boolean} Returns `true`, if the `value` is empty, else `false`.
   * @example
   *
   * _.isEmpty([1, 2, 3]);
   * // => false
   *
   * _.isEmpty({});
   * // => true
   *
   * _.isEmpty('');
   * // => true
   */
  function isEmpty(value) {
    var result = true;
    if (!value) {
      return result;
    }
    var className = toString.call(value),
        length = value.length;

    if ((className == arrayClass || className == stringClass ||
        className == argsClass || (noArgsClass && isArguments(value))) ||
        (className == objectClass && typeof length == 'number' && isFunction(value.splice))) {
      return !length;
    }
    forOwn(value, function() {
      return (result = false);
    });
    return result;
  }

  /**
   * Performs a deep comparison between two values to determine if they are
   * equivalent to each other. If `callback` is passed, it will be executed to
   * compare values. If `callback` returns `undefined`, comparisons will be handled
   * by the method instead. The `callback` is bound to `thisArg` and invoked with
   * two arguments; (a, b).
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} a The value to compare.
   * @param {Mixed} b The other value to compare.
   * @param {Function} [callback] The function to customize comparing values.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @param- {Object} [stackA=[]] Internally used track traversed `a` objects.
   * @param- {Object} [stackB=[]] Internally used track traversed `b` objects.
   * @returns {Boolean} Returns `true`, if the values are equvalent, else `false`.
   * @example
   *
   * var moe = { 'name': 'moe', 'age': 40 };
   * var copy = { 'name': 'moe', 'age': 40 };
   *
   * moe == copy;
   * // => false
   *
   * _.isEqual(moe, copy);
   * // => true
   *
   * var words = ['hello', 'goodbye'];
   * var otherWords = ['hi', 'goodbye'];
   *
   * _.isEqual(words, otherWords, function(a, b) {
   *   var reGreet = /^(?:hello|hi)$/i,
   *       aGreet = _.isString(a) && reGreet.test(a),
   *       bGreet = _.isString(b) && reGreet.test(b);
   *
   *   return (aGreet || bGreet) ? (aGreet == bGreet) : undefined;
   * });
   * // => true
   */
  function isEqual(a, b, callback, thisArg, stackA, stackB) {
    // used to indicate that when comparing objects, `a` has at least the properties of `b`
    var whereIndicator = callback === indicatorObject;
    if (callback && !whereIndicator) {
      callback = typeof thisArg == 'undefined' ? callback : createCallback(callback, thisArg, 2);
      var result = callback(a, b);
      if (typeof result != 'undefined') {
        return !!result;
      }
    }
    // exit early for identical values
    if (a === b) {
      // treat `+0` vs. `-0` as not equal
      return a !== 0 || (1 / a == 1 / b);
    }
    var type = typeof a,
        otherType = typeof b;

    // exit early for unlike primitive values
    if (a === a &&
        (!a || (type != 'function' && type != 'object')) &&
        (!b || (otherType != 'function' && otherType != 'object'))) {
      return false;
    }
    // exit early for `null` and `undefined`, avoiding ES3's Function#call behavior
    // http://es5.github.com/#x15.3.4.4
    if (a == null || b == null) {
      return a === b;
    }
    // compare [[Class]] names
    var className = toString.call(a),
        otherClass = toString.call(b);

    if (className == argsClass) {
      className = objectClass;
    }
    if (otherClass == argsClass) {
      otherClass = objectClass;
    }
    if (className != otherClass) {
      return false;
    }
    switch (className) {
      case boolClass:
      case dateClass:
        // coerce dates and booleans to numbers, dates to milliseconds and booleans
        // to `1` or `0`, treating invalid dates coerced to `NaN` as not equal
        return +a == +b;

      case numberClass:
        // treat `NaN` vs. `NaN` as equal
        return a != +a
          ? b != +b
          // but treat `+0` vs. `-0` as not equal
          : (a == 0 ? (1 / a == 1 / b) : a == +b);

      case regexpClass:
      case stringClass:
        // coerce regexes to strings (http://es5.github.com/#x15.10.6.4)
        // treat string primitives and their corresponding object instances as equal
        return a == b + '';
    }
    var isArr = className == arrayClass;
    if (!isArr) {
      // unwrap any `lodash` wrapped values
      if (a.__wrapped__ || b.__wrapped__) {
        return isEqual(a.__wrapped__ || a, b.__wrapped__ || b, callback, thisArg, stackA, stackB);
      }
      // exit for functions and DOM nodes
      if (className != objectClass || (noNodeClass && (isNode(a) || isNode(b)))) {
        return false;
      }
      // in older versions of Opera, `arguments` objects have `Array` constructors
      var ctorA = !argsAreObjects && isArguments(a) ? Object : a.constructor,
          ctorB = !argsAreObjects && isArguments(b) ? Object : b.constructor;

      // non `Object` object instances with different constructors are not equal
      if (ctorA != ctorB && !(
            isFunction(ctorA) && ctorA instanceof ctorA &&
            isFunction(ctorB) && ctorB instanceof ctorB
          )) {
        return false;
      }
    }
    // assume cyclic structures are equal
    // the algorithm for detecting cyclic structures is adapted from ES 5.1
    // section 15.12.3, abstract operation `JO` (http://es5.github.com/#x15.12.3)
    stackA || (stackA = []);
    stackB || (stackB = []);

    var length = stackA.length;
    while (length--) {
      if (stackA[length] == a) {
        return stackB[length] == b;
      }
    }
    var size = 0;
    result = true;

    // add `a` and `b` to the stack of traversed objects
    stackA.push(a);
    stackB.push(b);

    // recursively compare objects and arrays (susceptible to call stack limits)
    if (isArr) {
      length = a.length;
      size = b.length;

      // compare lengths to determine if a deep comparison is necessary
      result = size == a.length;
      if (!result && !whereIndicator) {
        return result;
      }
      // deep compare the contents, ignoring non-numeric properties
      while (size--) {
        var index = length,
            value = b[size];

        if (whereIndicator) {
          while (index--) {
            if ((result = isEqual(a[index], value, callback, thisArg, stackA, stackB))) {
              break;
            }
          }
        } else if (!(result = isEqual(a[size], value, callback, thisArg, stackA, stackB))) {
          break;
        }
      }
      return result;
    }
    // deep compare objects using `forIn`, instead of `forOwn`, to avoid `Object.keys`
    // which, in this case, is more costly
    forIn(b, function(value, key, b) {
      if (hasOwnProperty.call(b, key)) {
        // count the number of properties.
        size++;
        // deep compare each property value.
        return (result = hasOwnProperty.call(a, key) && isEqual(a[key], value, callback, thisArg, stackA, stackB));
      }
    });

    if (result && !whereIndicator) {
      // ensure both objects have the same number of properties
      forIn(a, function(value, key, a) {
        if (hasOwnProperty.call(a, key)) {
          // `size` will be `-1` if `a` has more properties than `b`
          return (result = --size > -1);
        }
      });
    }
    return result;
  }

  /**
   * Checks if `value` is, or can be coerced to, a finite number.
   *
   * Note: This is not the same as native `isFinite`, which will return true for
   * booleans and empty strings. See http://es5.github.com/#x15.1.2.5.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is finite, else `false`.
   * @example
   *
   * _.isFinite(-101);
   * // => true
   *
   * _.isFinite('10');
   * // => true
   *
   * _.isFinite(true);
   * // => false
   *
   * _.isFinite('');
   * // => false
   *
   * _.isFinite(Infinity);
   * // => false
   */
  function isFinite(value) {
    return nativeIsFinite(value) && !nativeIsNaN(parseFloat(value));
  }

  /**
   * Checks if `value` is a function.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a function, else `false`.
   * @example
   *
   * _.isFunction(_);
   * // => true
   */
  function isFunction(value) {
    return typeof value == 'function';
  }
  // fallback for older versions of Chrome and Safari
  if (isFunction(/x/)) {
    isFunction = function(value) {
      return value instanceof Function || toString.call(value) == funcClass;
    };
  }

  /**
   * Checks if `value` is the language type of Object.
   * (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is an object, else `false`.
   * @example
   *
   * _.isObject({});
   * // => true
   *
   * _.isObject([1, 2, 3]);
   * // => true
   *
   * _.isObject(1);
   * // => false
   */
  function isObject(value) {
    // check if the value is the ECMAScript language type of Object
    // http://es5.github.com/#x8
    // and avoid a V8 bug
    // http://code.google.com/p/v8/issues/detail?id=2291
    return value ? objectTypes[typeof value] : false;
  }

  /**
   * Checks if `value` is `NaN`.
   *
   * Note: This is not the same as native `isNaN`, which will return `true` for
   * `undefined` and other values. See http://es5.github.com/#x15.1.2.4.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is `NaN`, else `false`.
   * @example
   *
   * _.isNaN(NaN);
   * // => true
   *
   * _.isNaN(new Number(NaN));
   * // => true
   *
   * isNaN(undefined);
   * // => true
   *
   * _.isNaN(undefined);
   * // => false
   */
  function isNaN(value) {
    // `NaN` as a primitive is the only value that is not equal to itself
    // (perform the [[Class]] check first to avoid errors with some host objects in IE)
    return isNumber(value) && value != +value
  }

  /**
   * Checks if `value` is `null`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is `null`, else `false`.
   * @example
   *
   * _.isNull(null);
   * // => true
   *
   * _.isNull(undefined);
   * // => false
   */
  function isNull(value) {
    return value === null;
  }

  /**
   * Checks if `value` is a number.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a number, else `false`.
   * @example
   *
   * _.isNumber(8.4 * 5);
   * // => true
   */
  function isNumber(value) {
    return typeof value == 'number' || toString.call(value) == numberClass;
  }

  /**
   * Checks if a given `value` is an object created by the `Object` constructor.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if `value` is a plain object, else `false`.
   * @example
   *
   * function Stooge(name, age) {
   *   this.name = name;
   *   this.age = age;
   * }
   *
   * _.isPlainObject(new Stooge('moe', 40));
   * // => false
   *
   * _.isPlainObject([1, 2, 3]);
   * // => false
   *
   * _.isPlainObject({ 'name': 'moe', 'age': 40 });
   * // => true
   */
  var isPlainObject = !getPrototypeOf ? shimIsPlainObject : function(value) {
    if (!(value && typeof value == 'object')) {
      return false;
    }
    var valueOf = value.valueOf,
        objProto = typeof valueOf == 'function' && (objProto = getPrototypeOf(valueOf)) && getPrototypeOf(objProto);

    return objProto
      ? value == objProto || (getPrototypeOf(value) == objProto && !isArguments(value))
      : shimIsPlainObject(value);
  };

  /**
   * Checks if `value` is a regular expression.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a regular expression, else `false`.
   * @example
   *
   * _.isRegExp(/moe/);
   * // => true
   */
  function isRegExp(value) {
    return value instanceof RegExp || toString.call(value) == regexpClass;
  }

  /**
   * Checks if `value` is a string.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is a string, else `false`.
   * @example
   *
   * _.isString('moe');
   * // => true
   */
  function isString(value) {
    return typeof value == 'string' || toString.call(value) == stringClass;
  }

  /**
   * Checks if `value` is `undefined`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Mixed} value The value to check.
   * @returns {Boolean} Returns `true`, if the `value` is `undefined`, else `false`.
   * @example
   *
   * _.isUndefined(void 0);
   * // => true
   */
  function isUndefined(value) {
    return typeof value == 'undefined';
  }

  /**
   * Recursively merges own enumerable properties of the source object(s), that
   * don't resolve to `undefined`, into the destination object. Subsequent sources
   * will overwrite propery assignments of previous sources. If a `callback` function
   * is passed, it will be executed to produce the merged values of the destination
   * and source properties. If `callback` returns `undefined`, merging will be
   * handled by the method instead. The `callback` is bound to `thisArg` and
   * invoked with two arguments; (objectValue, sourceValue).
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The destination object.
   * @param {Object} [source1, source2, ...] The source objects.
   * @param {Function} [callback] The function to customize merging properties.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @param- {Object} [deepIndicator] Internally used to indicate that `stackA`
   *  and `stackB` are arrays of traversed objects instead of source objects.
   * @param- {Array} [stackA=[]] Internally used to track traversed source objects.
   * @param- {Array} [stackB=[]] Internally used to associate values with their
   *  source counterparts.
   * @returns {Object} Returns the destination object.
   * @example
   *
   * var names = {
   *   'stooges': [
   *     { 'name': 'moe' },
   *     { 'name': 'larry' }
   *   ]
   * };
   *
   * var ages = {
   *   'stooges': [
   *     { 'age': 40 },
   *     { 'age': 50 }
   *   ]
   * };
   *
   * _.merge(names, ages);
   * // => { 'stooges': [{ 'name': 'moe', 'age': 40 }, { 'name': 'larry', 'age': 50 }] }
   *
   * var food = {
   *   'fruits': ['apple'],
   *   'vegetables': ['beet']
   * };
   *
   * var otherFood = {
   *   'fruits': ['banana'],
   *   'vegetables': ['carrot']
   * };
   *
   * _.merge(food, otherFood, function(a, b) {
   *   return _.isArray(a) ? a.concat(b) : undefined;
   * });
   * // => { 'fruits': ['apple', 'banana'], 'vegetables': ['beet', 'carrot] }
   */
  function merge(object, source, deepIndicator) {
    var args = arguments,
        index = 0,
        length = 2;

    if (!isObject(object)) {
      return object;
    }
    if (deepIndicator === indicatorObject) {
      var callback = args[3],
          stackA = args[4],
          stackB = args[5];
    } else {
      stackA = [];
      stackB = [];

      // allows working with `_.reduce` and `_.reduceRight` without
      // using their `callback` arguments, `index|key` and `collection`
      if (typeof deepIndicator != 'number') {
        length = args.length;
      }
      if (length > 3 && typeof args[length - 2] == 'function') {
        callback = createCallback(args[--length - 1], args[length--], 2);
      } else if (length > 2 && typeof args[length - 1] == 'function') {
        callback = args[--length];
      }
    }
    while (++index < length) {
      (isArray(args[index]) ? forEach : forOwn)(args[index], function(source, key) {
        var found,
            isArr,
            result = source,
            value = object[key];

        if (source && ((isArr = isArray(source)) || isPlainObject(source))) {
          // avoid merging previously merged cyclic sources
          var stackLength = stackA.length;
          while (stackLength--) {
            if ((found = stackA[stackLength] == source)) {
              value = stackB[stackLength];
              break;
            }
          }
          if (!found) {
            value = isArr
              ? (isArray(value) ? value : [])
              : (isPlainObject(value) ? value : {});

            if (callback) {
              result = callback(value, source);
              if (typeof result != 'undefined') {
                value = result;
              }
            }
            // add `source` and associated `value` to the stack of traversed objects
            stackA.push(source);
            stackB.push(value);

            // recursively merge objects and arrays (susceptible to call stack limits)
            if (!callback) {
              value = merge(value, source, indicatorObject, callback, stackA, stackB);
            }
          }
        }
        else {
          if (callback) {
            result = callback(value, source);
            if (typeof result == 'undefined') {
              result = source;
            }
          }
          if (typeof result != 'undefined') {
            value = result;
          }
        }
        object[key] = value;
      });
    }
    return object;
  }

  /**
   * Creates a shallow clone of `object` excluding the specified properties.
   * Property names may be specified as individual arguments or as arrays of
   * property names. If a `callback` function is passed, it will be executed
   * for each property in the `object`, omitting the properties `callback`
   * returns truthy for. The `callback` is bound to `thisArg` and invoked
   * with three arguments; (value, key, object).
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The source object.
   * @param {Function|String} callback|[prop1, prop2, ...] The properties to omit
   *  or the function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns an object without the omitted properties.
   * @example
   *
   * _.omit({ 'name': 'moe', 'age': 40 }, 'age');
   * // => { 'name': 'moe' }
   *
   * _.omit({ 'name': 'moe', 'age': 40 }, function(value) {
   *   return typeof value == 'number';
   * });
   * // => { 'name': 'moe' }
   */
  function omit(object, callback, thisArg) {
    var isFunc = typeof callback == 'function',
        result = {};

    if (isFunc) {
      callback = createCallback(callback, thisArg);
    } else {
      var props = concat.apply(arrayRef, arguments);
    }
    forIn(object, function(value, key, object) {
      if (isFunc
            ? !callback(value, key, object)
            : indexOf(props, key, 1) < 0
          ) {
        result[key] = value;
      }
    });
    return result;
  }

  /**
   * Creates a two dimensional array of the given object's key-value pairs,
   * i.e. `[[key1, value1], [key2, value2]]`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The object to inspect.
   * @returns {Array} Returns new array of key-value pairs.
   * @example
   *
   * _.pairs({ 'moe': 30, 'larry': 40 });
   * // => [['moe', 30], ['larry', 40]] (order is not guaranteed)
   */
  function pairs(object) {
    var index = -1,
        props = keys(object),
        length = props.length,
        result = Array(length);

    while (++index < length) {
      var key = props[index];
      result[index] = [key, object[key]];
    }
    return result;
  }

  /**
   * Creates a shallow clone of `object` composed of the specified properties.
   * Property names may be specified as individual arguments or as arrays of property
   * names. If `callback` is passed, it will be executed for each property in the
   * `object`, picking the properties `callback` returns truthy for. The `callback`
   * is bound to `thisArg` and invoked with three arguments; (value, key, object).
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The source object.
   * @param {Array|Function|String} callback|[prop1, prop2, ...] The function called
   *  per iteration or properties to pick, either as individual arguments or arrays.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns an object composed of the picked properties.
   * @example
   *
   * _.pick({ 'name': 'moe', '_userid': 'moe1' }, 'name');
   * // => { 'name': 'moe' }
   *
   * _.pick({ 'name': 'moe', '_userid': 'moe1' }, function(value, key) {
   *   return key.charAt(0) != '_';
   * });
   * // => { 'name': 'moe' }
   */
  function pick(object, callback, thisArg) {
    var result = {};
    if (typeof callback != 'function') {
      var index = 0,
          props = concat.apply(arrayRef, arguments),
          length = isObject(object) ? props.length : 0;

      while (++index < length) {
        var key = props[index];
        if (key in object) {
          result[key] = object[key];
        }
      }
    } else {
      callback = createCallback(callback, thisArg);
      forIn(object, function(value, key, object) {
        if (callback(value, key, object)) {
          result[key] = value;
        }
      });
    }
    return result;
  }

  /**
   * Creates an array composed of the own enumerable property values of `object`.
   *
   * @static
   * @memberOf _
   * @category Objects
   * @param {Object} object The object to inspect.
   * @returns {Array} Returns a new array of property values.
   * @example
   *
   * _.values({ 'one': 1, 'two': 2, 'three': 3 });
   * // => [1, 2, 3]
   */
  function values(object) {
    var index = -1,
        props = keys(object),
        length = props.length,
        result = Array(length);

    while (++index < length) {
      result[index] = object[props[index]];
    }
    return result;
  }

  /*--------------------------------------------------------------------------*/

  /**
   * Creates an array of elements from the specified indexes, or keys, of the
   * `collection`. Indexes may be specified as individual arguments or as arrays
   * of indexes.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Array|Number|String} [index1, index2, ...] The indexes of
   *  `collection` to retrieve, either as individual arguments or arrays.
   * @returns {Array} Returns a new array of elements corresponding to the
   *  provided indexes.
   * @example
   *
   * _.at(['a', 'b', 'c', 'd', 'e'], [0, 2, 4]);
   * // => ['a', 'c', 'e']
   *
   * _.at(['moe', 'larry', 'curly'], 0, 2);
   * // => ['moe', 'curly']
   */
  function at(collection) {
    var index = -1,
        props = concat.apply(arrayRef, slice(arguments, 1)),
        length = props.length,
        result = Array(length);

    if (noCharByIndex && isString(collection)) {
      collection = collection.split('');
    }
    while(++index < length) {
      result[index] = collection[props[index]];
    }
    return result;
  }

  /**
   * Checks if a given `target` element is present in a `collection` using strict
   * equality for comparisons, i.e. `===`. If `fromIndex` is negative, it is used
   * as the offset from the end of the collection.
   *
   * @static
   * @memberOf _
   * @alias include
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Mixed} target The value to check for.
   * @param {Number} [fromIndex=0] The index to search from.
   * @returns {Boolean} Returns `true` if the `target` element is found, else `false`.
   * @example
   *
   * _.contains([1, 2, 3], 1);
   * // => true
   *
   * _.contains([1, 2, 3], 1, 2);
   * // => false
   *
   * _.contains({ 'name': 'moe', 'age': 40 }, 'moe');
   * // => true
   *
   * _.contains('curly', 'ur');
   * // => true
   */
  function contains(collection, target, fromIndex) {
    var index = -1,
        length = collection ? collection.length : 0,
        result = false;

    fromIndex = (fromIndex < 0 ? nativeMax(0, length + fromIndex) : fromIndex) || 0;
    if (typeof length == 'number') {
      result = (isString(collection)
        ? collection.indexOf(target, fromIndex)
        : indexOf(collection, target, fromIndex)
      ) > -1;
    } else {
      each(collection, function(value) {
        if (++index >= fromIndex) {
          return !(result = value === target);
        }
      });
    }
    return result;
  }

  /**
   * Creates an object composed of keys returned from running each element of the
   * `collection` through the given `callback`. The corresponding value of each key
   * is the number of times the key was returned by the `callback`. The `callback`
   * is bound to `thisArg` and invoked with three arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns the composed aggregate object.
   * @example
   *
   * _.countBy([4.3, 6.1, 6.4], function(num) { return Math.floor(num); });
   * // => { '4': 1, '6': 2 }
   *
   * _.countBy([4.3, 6.1, 6.4], function(num) { return this.floor(num); }, Math);
   * // => { '4': 1, '6': 2 }
   *
   * _.countBy(['one', 'two', 'three'], 'length');
   * // => { '3': 2, '5': 1 }
   */
  function countBy(collection, callback, thisArg) {
    var result = {};
    callback = createCallback(callback, thisArg);

    forEach(collection, function(value, key, collection) {
      key = callback(value, key, collection) + '';
      (hasOwnProperty.call(result, key) ? result[key]++ : result[key] = 1);
    });
    return result;
  }

  /**
   * Checks if the `callback` returns a truthy value for **all** elements of a
   * `collection`. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias all
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Boolean} Returns `true` if all elements pass the callback check,
   *  else `false`.
   * @example
   *
   * _.every([true, 1, null, 'yes'], Boolean);
   * // => false
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.every(stooges, 'age');
   * // => true
   *
   * // using "_.where" callback shorthand
   * _.every(stooges, { 'age': 50 });
   * // => false
   */
  function every(collection, callback, thisArg) {
    var result = true;
    callback = createCallback(callback, thisArg);

    if (isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        if (!(result = !!callback(collection[index], index, collection))) {
          break;
        }
      }
    } else {
      each(collection, function(value, index, collection) {
        return (result = !!callback(value, index, collection));
      });
    }
    return result;
  }

  /**
   * Examines each element in a `collection`, returning an array of all elements
   * the `callback` returns truthy for. The `callback` is bound to `thisArg` and
   * invoked with three arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias select
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a new array of elements that passed the callback check.
   * @example
   *
   * var evens = _.filter([1, 2, 3, 4, 5, 6], function(num) { return num % 2 == 0; });
   * // => [2, 4, 6]
   *
   * var food = [
   *   { 'name': 'apple',  'organic': false, 'type': 'fruit' },
   *   { 'name': 'carrot', 'organic': true,  'type': 'vegetable' }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.filter(food, 'organic');
   * // => [{ 'name': 'carrot', 'organic': true, 'type': 'vegetable' }]
   *
   * // using "_.where" callback shorthand
   * _.filter(food, { 'type': 'fruit' });
   * // => [{ 'name': 'apple', 'organic': false, 'type': 'fruit' }]
   */
  function filter(collection, callback, thisArg) {
    var result = [];
    callback = createCallback(callback, thisArg);

    if (isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        var value = collection[index];
        if (callback(value, index, collection)) {
          result.push(value);
        }
      }
    } else {
      each(collection, function(value, index, collection) {
        if (callback(value, index, collection)) {
          result.push(value);
        }
      });
    }
    return result;
  }

  /**
   * Examines each element in a `collection`, returning the first that the `callback`
   * returns truthy for. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias detect
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the element that passed the callback check,
   *  else `undefined`.
   * @example
   *
   * var even = _.find([1, 2, 3, 4, 5, 6], function(num) { return num % 2 == 0; });
   * // => 2
   *
   * var food = [
   *   { 'name': 'apple',  'organic': false, 'type': 'fruit' },
   *   { 'name': 'banana', 'organic': true,  'type': 'fruit' },
   *   { 'name': 'beet',   'organic': false, 'type': 'vegetable' },
   *   { 'name': 'carrot', 'organic': true,  'type': 'vegetable' }
   * ];
   *
   * // using "_.where" callback shorthand
   * var veggie = _.find(food, { 'type': 'vegetable' });
   * // => { 'name': 'beet', 'organic': false, 'type': 'vegetable' }
   *
   * // using "_.pluck" callback shorthand
   * var healthy = _.find(food, 'organic');
   * // => { 'name': 'banana', 'organic': true, 'type': 'fruit' }
   */
  function find(collection, callback, thisArg) {
    var result;
    callback = createCallback(callback, thisArg);

    forEach(collection, function(value, index, collection) {
      if (callback(value, index, collection)) {
        result = value;
        return false;
      }
    });
    return result;
  }

  /**
   * Iterates over a `collection`, executing the `callback` for each element in
   * the `collection`. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, index|key, collection). Callbacks may exit iteration early
   * by explicitly returning `false`.
   *
   * @static
   * @memberOf _
   * @alias each
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array|Object|String} Returns `collection`.
   * @example
   *
   * _([1, 2, 3]).forEach(alert).join(',');
   * // => alerts each number and returns '1,2,3'
   *
   * _.forEach({ 'one': 1, 'two': 2, 'three': 3 }, alert);
   * // => alerts each number value (order is not guaranteed)
   */
  function forEach(collection, callback, thisArg) {
    if (callback && typeof thisArg == 'undefined' && isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        if (callback(collection[index], index, collection) === false) {
          break;
        }
      }
    } else {
      each(collection, callback, thisArg);
    }
    return collection;
  }

  /**
   * Creates an object composed of keys returned from running each element of the
   * `collection` through the `callback`. The corresponding value of each key is
   * an array of elements passed to `callback` that returned the key. The `callback`
   * is bound to `thisArg` and invoked with three arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Object} Returns the composed aggregate object.
   * @example
   *
   * _.groupBy([4.2, 6.1, 6.4], function(num) { return Math.floor(num); });
   * // => { '4': [4.2], '6': [6.1, 6.4] }
   *
   * _.groupBy([4.2, 6.1, 6.4], function(num) { return this.floor(num); }, Math);
   * // => { '4': [4.2], '6': [6.1, 6.4] }
   *
   * // using "_.pluck" callback shorthand
   * _.groupBy(['one', 'two', 'three'], 'length');
   * // => { '3': ['one', 'two'], '5': ['three'] }
   */
  function groupBy(collection, callback, thisArg) {
    var result = {};
    callback = createCallback(callback, thisArg);

    forEach(collection, function(value, key, collection) {
      key = callback(value, key, collection) + '';
      (hasOwnProperty.call(result, key) ? result[key] : result[key] = []).push(value);
    });
    return result;
  }

  /**
   * Invokes the method named by `methodName` on each element in the `collection`,
   * returning an array of the results of each invoked method. Additional arguments
   * will be passed to each invoked method. If `methodName` is a function, it will
   * be invoked for, and `this` bound to, each element in the `collection`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|String} methodName The name of the method to invoke or
   *  the function invoked per iteration.
   * @param {Mixed} [arg1, arg2, ...] Arguments to invoke the method with.
   * @returns {Array} Returns a new array of the results of each invoked method.
   * @example
   *
   * _.invoke([[5, 1, 7], [3, 2, 1]], 'sort');
   * // => [[1, 5, 7], [1, 2, 3]]
   *
   * _.invoke([123, 456], String.prototype.split, '');
   * // => [['1', '2', '3'], ['4', '5', '6']]
   */
  function invoke(collection, methodName) {
    var args = slice(arguments, 2),
        index = -1,
        isFunc = typeof methodName == 'function',
        length = collection ? collection.length : 0,
        result = Array(typeof length == 'number' ? length : 0);

    forEach(collection, function(value) {
      result[++index] = (isFunc ? methodName : value[methodName]).apply(value, args);
    });
    return result;
  }

  /**
   * Creates an array of values by running each element in the `collection`
   * through the `callback`. The `callback` is bound to `thisArg` and invoked with
   * three arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias collect
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a new array of the results of each `callback` execution.
   * @example
   *
   * _.map([1, 2, 3], function(num) { return num * 3; });
   * // => [3, 6, 9]
   *
   * _.map({ 'one': 1, 'two': 2, 'three': 3 }, function(num) { return num * 3; });
   * // => [3, 6, 9] (order is not guaranteed)
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.map(stooges, 'name');
   * // => ['moe', 'larry']
   */
  function map(collection, callback, thisArg) {
    var index = -1,
        length = collection ? collection.length : 0,
        result = Array(typeof length == 'number' ? length : 0);

    callback = createCallback(callback, thisArg);
    if (isArray(collection)) {
      while (++index < length) {
        result[index] = callback(collection[index], index, collection);
      }
    } else {
      each(collection, function(value, key, collection) {
        result[++index] = callback(value, key, collection);
      });
    }
    return result;
  }

  /**
   * Retrieves the maximum value of an `array`. If `callback` is passed,
   * it will be executed for each value in the `array` to generate the
   * criterion by which the value is ranked. The `callback` is bound to
   * `thisArg` and invoked with three arguments; (value, index, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the maximum value.
   * @example
   *
   * _.max([4, 2, 8, 6]);
   * // => 8
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * _.max(stooges, function(stooge) { return stooge.age; });
   * // => { 'name': 'larry', 'age': 50 };
   *
   * // using "_.pluck" callback shorthand
   * _.max(stooges, 'age');
   * // => { 'name': 'larry', 'age': 50 };
   */
  function max(collection, callback, thisArg) {
    var computed = -Infinity,
        result = computed;

    if (!callback && isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        var value = collection[index];
        if (value > result) {
          result = value;
        }
      }
    } else {
      callback = !callback && isString(collection)
        ? charAtCallback
        : createCallback(callback, thisArg);

      each(collection, function(value, index, collection) {
        var current = callback(value, index, collection);
        if (current > computed) {
          computed = current;
          result = value;
        }
      });
    }
    return result;
  }

  /**
   * Retrieves the minimum value of an `array`. If `callback` is passed,
   * it will be executed for each value in the `array` to generate the
   * criterion by which the value is ranked. The `callback` is bound to `thisArg`
   * and invoked with three arguments; (value, index, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the minimum value.
   * @example
   *
   * _.min([4, 2, 8, 6]);
   * // => 2
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * _.min(stooges, function(stooge) { return stooge.age; });
   * // => { 'name': 'moe', 'age': 40 };
   *
   * // using "_.pluck" callback shorthand
   * _.min(stooges, 'age');
   * // => { 'name': 'moe', 'age': 40 };
   */
  function min(collection, callback, thisArg) {
    var computed = Infinity,
        result = computed;

    if (!callback && isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        var value = collection[index];
        if (value < result) {
          result = value;
        }
      }
    } else {
      callback = !callback && isString(collection)
        ? charAtCallback
        : createCallback(callback, thisArg);

      each(collection, function(value, index, collection) {
        var current = callback(value, index, collection);
        if (current < computed) {
          computed = current;
          result = value;
        }
      });
    }
    return result;
  }

  /**
   * Retrieves the value of a specified property from all elements in the `collection`.
   *
   * @static
   * @memberOf _
   * @type Function
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {String} property The property to pluck.
   * @returns {Array} Returns a new array of property values.
   * @example
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * _.pluck(stooges, 'name');
   * // => ['moe', 'larry']
   */
  var pluck = map;

  /**
   * Reduces a `collection` to a value that is the accumulated result of running
   * each element in the `collection` through the `callback`, where each successive
   * `callback` execution consumes the return value of the previous execution.
   * If `accumulator` is not passed, the first element of the `collection` will be
   * used as the initial `accumulator` value. The `callback` is bound to `thisArg`
   * and invoked with four arguments; (accumulator, value, index|key, collection).
   *
   * @static
   * @memberOf _
   * @alias foldl, inject
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [accumulator] Initial value of the accumulator.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the accumulated value.
   * @example
   *
   * var sum = _.reduce([1, 2, 3], function(sum, num) {
   *   return sum + num;
   * });
   * // => 6
   *
   * var mapped = _.reduce({ 'a': 1, 'b': 2, 'c': 3 }, function(result, num, key) {
   *   result[key] = num * 3;
   *   return result;
   * }, {});
   * // => { 'a': 3, 'b': 6, 'c': 9 }
   */
  function reduce(collection, callback, accumulator, thisArg) {
    var noaccum = arguments.length < 3;
    callback = createCallback(callback, thisArg, 4);

    if (isArray(collection)) {
      var index = -1,
          length = collection.length;

      if (noaccum) {
        accumulator = collection[++index];
      }
      while (++index < length) {
        accumulator = callback(accumulator, collection[index], index, collection);
      }
    } else {
      each(collection, function(value, index, collection) {
        accumulator = noaccum
          ? (noaccum = false, value)
          : callback(accumulator, value, index, collection)
      });
    }
    return accumulator;
  }

  /**
   * This method is similar to `_.reduce`, except that it iterates over a
   * `collection` from right to left.
   *
   * @static
   * @memberOf _
   * @alias foldr
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function} [callback=identity] The function called per iteration.
   * @param {Mixed} [accumulator] Initial value of the accumulator.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the accumulated value.
   * @example
   *
   * var list = [[0, 1], [2, 3], [4, 5]];
   * var flat = _.reduceRight(list, function(a, b) { return a.concat(b); }, []);
   * // => [4, 5, 2, 3, 0, 1]
   */
  function reduceRight(collection, callback, accumulator, thisArg) {
    var iterable = collection,
        length = collection ? collection.length : 0,
        noaccum = arguments.length < 3;

    if (typeof length != 'number') {
      var props = keys(collection);
      length = props.length;
    } else if (noCharByIndex && isString(collection)) {
      iterable = collection.split('');
    }
    callback = createCallback(callback, thisArg, 4);
    forEach(collection, function(value, index, collection) {
      index = props ? props[--length] : --length;
      accumulator = noaccum
        ? (noaccum = false, iterable[index])
        : callback(accumulator, iterable[index], index, collection);
    });
    return accumulator;
  }

  /**
   * The opposite of `_.filter`, this method returns the elements of a
   * `collection` that `callback` does **not** return truthy for.
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a new array of elements that did **not** pass the
   *  callback check.
   * @example
   *
   * var odds = _.reject([1, 2, 3, 4, 5, 6], function(num) { return num % 2 == 0; });
   * // => [1, 3, 5]
   *
   * var food = [
   *   { 'name': 'apple',  'organic': false, 'type': 'fruit' },
   *   { 'name': 'carrot', 'organic': true,  'type': 'vegetable' }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.reject(food, 'organic');
   * // => [{ 'name': 'apple', 'organic': false, 'type': 'fruit' }]
   *
   * // using "_.where" callback shorthand
   * _.reject(food, { 'type': 'fruit' });
   * // => [{ 'name': 'carrot', 'organic': true, 'type': 'vegetable' }]
   */
  function reject(collection, callback, thisArg) {
    callback = createCallback(callback, thisArg);
    return filter(collection, function(value, index, collection) {
      return !callback(value, index, collection);
    });
  }

  /**
   * Creates an array of shuffled `array` values, using a version of the
   * Fisher-Yates shuffle. See http://en.wikipedia.org/wiki/Fisher-Yates_shuffle.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to shuffle.
   * @returns {Array} Returns a new shuffled collection.
   * @example
   *
   * _.shuffle([1, 2, 3, 4, 5, 6]);
   * // => [4, 1, 6, 3, 5, 2]
   */
  function shuffle(collection) {
    var index = -1,
        length = collection ? collection.length : 0,
        result = Array(typeof length == 'number' ? length : 0);

    forEach(collection, function(value) {
      var rand = floor(nativeRandom() * (++index + 1));
      result[index] = result[rand];
      result[rand] = value;
    });
    return result;
  }

  /**
   * Gets the size of the `collection` by returning `collection.length` for arrays
   * and array-like objects or the number of own enumerable properties for objects.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to inspect.
   * @returns {Number} Returns `collection.length` or number of own enumerable properties.
   * @example
   *
   * _.size([1, 2]);
   * // => 2
   *
   * _.size({ 'one': 1, 'two': 2, 'three': 3 });
   * // => 3
   *
   * _.size('curly');
   * // => 5
   */
  function size(collection) {
    var length = collection ? collection.length : 0;
    return typeof length == 'number' ? length : keys(collection).length;
  }

  /**
   * Checks if the `callback` returns a truthy value for **any** element of a
   * `collection`. The function returns as soon as it finds passing value, and
   * does not iterate over the entire `collection`. The `callback` is bound to
   * `thisArg` and invoked with three arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias any
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Boolean} Returns `true` if any element passes the callback check,
   *  else `false`.
   * @example
   *
   * _.some([null, 0, 'yes', false], Boolean);
   * // => true
   *
   * var food = [
   *   { 'name': 'apple',  'organic': false, 'type': 'fruit' },
   *   { 'name': 'carrot', 'organic': true,  'type': 'vegetable' }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.some(food, 'organic');
   * // => true
   *
   * // using "_.where" callback shorthand
   * _.some(food, { 'type': 'meat' });
   * // => false
   */
  function some(collection, callback, thisArg) {
    var result;
    callback = createCallback(callback, thisArg);

    if (isArray(collection)) {
      var index = -1,
          length = collection.length;

      while (++index < length) {
        if ((result = callback(collection[index], index, collection))) {
          break;
        }
      }
    } else {
      each(collection, function(value, index, collection) {
        return !(result = callback(value, index, collection));
      });
    }
    return !!result;
  }

  /**
   * Creates an array of elements, sorted in ascending order by the results of
   * running each element in the `collection` through the `callback`. This method
   * performs a stable sort, that is, it will preserve the original sort order of
   * equal elements. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, index|key, collection).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a new array of sorted elements.
   * @example
   *
   * _.sortBy([1, 2, 3], function(num) { return Math.sin(num); });
   * // => [3, 1, 2]
   *
   * _.sortBy([1, 2, 3], function(num) { return this.sin(num); }, Math);
   * // => [3, 1, 2]
   *
   * // using "_.pluck" callback shorthand
   * _.sortBy(['banana', 'strawberry', 'apple'], 'length');
   * // => ['apple', 'banana', 'strawberry']
   */
  function sortBy(collection, callback, thisArg) {
    var index = -1,
        length = collection ? collection.length : 0,
        result = Array(typeof length == 'number' ? length : 0);

    callback = createCallback(callback, thisArg);
    forEach(collection, function(value, key, collection) {
      result[++index] = {
        'criteria': callback(value, key, collection),
        'index': index,
        'value': value
      };
    });

    length = result.length;
    result.sort(compareAscending);
    while (length--) {
      result[length] = result[length].value;
    }
    return result;
  }

  /**
   * Converts the `collection` to an array.
   *
   * @static
   * @memberOf _
   * @category Collections
   * @param {Array|Object|String} collection The collection to convert.
   * @returns {Array} Returns the new converted array.
   * @example
   *
   * (function() { return _.toArray(arguments).slice(1); })(1, 2, 3, 4);
   * // => [2, 3, 4]
   */
  function toArray(collection) {
    if (collection && typeof collection.length == 'number') {
      return noCharByIndex && isString(collection)
        ? collection.split('')
        : slice(collection);
    }
    return values(collection);
  }

  /**
   * Examines each element in a `collection`, returning an array of all elements
   * that have the given `properties`. When checking `properties`, this method
   * performs a deep comparison between values to determine if they are equivalent
   * to each other.
   *
   * @static
   * @memberOf _
   * @type Function
   * @category Collections
   * @param {Array|Object|String} collection The collection to iterate over.
   * @param {Object} properties The object of property values to filter by.
   * @returns {Array} Returns a new array of elements that have the given `properties`.
   * @example
   *
   * var stooges = [
   *   { 'name': 'moe', 'age': 40 },
   *   { 'name': 'larry', 'age': 50 }
   * ];
   *
   * _.where(stooges, { 'age': 40 });
   * // => [{ 'name': 'moe', 'age': 40 }]
   */
  var where = filter;

  /*--------------------------------------------------------------------------*/

  /**
   * Creates an array with all falsey values of `array` removed. The values
   * `false`, `null`, `0`, `""`, `undefined` and `NaN` are all falsey.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to compact.
   * @returns {Array} Returns a new filtered array.
   * @example
   *
   * _.compact([0, 1, false, 2, '', 3]);
   * // => [1, 2, 3]
   */
  function compact(array) {
    var index = -1,
        length = array ? array.length : 0,
        result = [];

    while (++index < length) {
      var value = array[index];
      if (value) {
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Creates an array of `array` elements not present in the other arrays
   * using strict equality for comparisons, i.e. `===`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to process.
   * @param {Array} [array1, array2, ...] Arrays to check.
   * @returns {Array} Returns a new array of `array` elements not present in the
   *  other arrays.
   * @example
   *
   * _.difference([1, 2, 3, 4, 5], [5, 2, 10]);
   * // => [1, 3, 4]
   */
  function difference(array) {
    var index = -1,
        length = array ? array.length : 0,
        flattened = concat.apply(arrayRef, arguments),
        contains = cachedContains(flattened, length),
        result = [];

    while (++index < length) {
      var value = array[index];
      if (!contains(value)) {
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Gets the first element of the `array`. If a number `n` is passed, the first
   * `n` elements of the `array` are returned. If a `callback` function is passed,
   * the first elements the `callback` returns truthy for are returned. The `callback`
   * is bound to `thisArg` and invoked with three arguments; (value, index, array).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias head, take
   * @category Arrays
   * @param {Array} array The array to query.
   * @param {Function|Object|Number|String} [callback|n] The function called
   *  per element or the number of elements to return. If a property name or
   *  object is passed, it will be used to create a "_.pluck" or "_.where"
   *  style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the first element(s) of `array`.
   * @example
   *
   * _.first([1, 2, 3]);
   * // => 1
   *
   * _.first([1, 2, 3], 2);
   * // => [1, 2]
   *
   * _.first([1, 2, 3], function(num) {
   *   return num < 3;
   * });
   * // => [1, 2]
   *
   * var food = [
   *   { 'name': 'banana', 'organic': true },
   *   { 'name': 'beet',   'organic': false },
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.first(food, 'organic');
   * // => [{ 'name': 'banana', 'organic': true }]
   *
   * var food = [
   *   { 'name': 'apple',  'type': 'fruit' },
   *   { 'name': 'banana', 'type': 'fruit' },
   *   { 'name': 'beet',   'type': 'vegetable' }
   * ];
   *
   * // using "_.where" callback shorthand
   * _.first(food, { 'type': 'fruit' });
   * // => [{ 'name': 'apple', 'type': 'fruit' }, { 'name': 'banana', 'type': 'fruit' }]
   */
  function first(array, callback, thisArg) {
    if (array) {
      var n = 0,
          length = array.length;

      if (typeof callback != 'number' && callback != null) {
        var index = -1;
        callback = createCallback(callback, thisArg);
        while (++index < length && callback(array[index], index, array)) {
          n++;
        }
      } else {
        n = callback;
        if (n == null || thisArg) {
          return array[0];
        }
      }
      return slice(array, 0, nativeMin(nativeMax(0, n), length));
    }
  }

  /**
   * Flattens a nested array (the nesting can be to any depth). If `shallow` is
   * truthy, `array` will only be flattened a single level.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to compact.
   * @param {Boolean} shallow A flag to indicate only flattening a single level.
   * @returns {Array} Returns a new flattened array.
   * @example
   *
   * _.flatten([1, [2], [3, [[4]]]]);
   * // => [1, 2, 3, 4];
   *
   * _.flatten([1, [2], [3, [[4]]]], true);
   * // => [1, 2, 3, [[4]]];
   */
  function flatten(array, shallow) {
    var index = -1,
        length = array ? array.length : 0,
        result = [];

    while (++index < length) {
      var value = array[index];

      // recursively flatten arrays (susceptible to call stack limits)
      if (isArray(value)) {
        push.apply(result, shallow ? value : flatten(value));
      } else {
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Gets the index at which the first occurrence of `value` is found using
   * strict equality for comparisons, i.e. `===`. If the `array` is already
   * sorted, passing `true` for `fromIndex` will run a faster binary search.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to search.
   * @param {Mixed} value The value to search for.
   * @param {Boolean|Number} [fromIndex=0] The index to search from or `true` to
   *  perform a binary search on a sorted `array`.
   * @returns {Number} Returns the index of the matched value or `-1`.
   * @example
   *
   * _.indexOf([1, 2, 3, 1, 2, 3], 2);
   * // => 1
   *
   * _.indexOf([1, 2, 3, 1, 2, 3], 2, 3);
   * // => 4
   *
   * _.indexOf([1, 1, 2, 2, 3, 3], 2, true);
   * // => 2
   */
  function indexOf(array, value, fromIndex) {
    var index = -1,
        length = array ? array.length : 0;

    if (typeof fromIndex == 'number') {
      index = (fromIndex < 0 ? nativeMax(0, length + fromIndex) : fromIndex || 0) - 1;
    } else if (fromIndex) {
      index = sortedIndex(array, value);
      return array[index] === value ? index : -1;
    }
    while (++index < length) {
      if (array[index] === value) {
        return index;
      }
    }
    return -1;
  }

  /**
   * Gets all but the last element of `array`. If a number `n` is passed, the
   * last `n` elements are excluded from the result. If a `callback` function
   * is passed, the last elements the `callback` returns truthy for are excluded
   * from the result. The `callback` is bound to `thisArg` and invoked with three
   * arguments; (value, index, array).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to query.
   * @param {Function|Object|Number|String} [callback|n=1] The function called
   *  per element or the number of elements to exclude. If a property name or
   *  object is passed, it will be used to create a "_.pluck" or "_.where"
   *  style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a slice of `array`.
   * @example
   *
   * _.initial([1, 2, 3]);
   * // => [1, 2]
   *
   * _.initial([1, 2, 3], 2);
   * // => [1]
   *
   * _.initial([1, 2, 3], function(num) {
   *   return num > 1;
   * });
   * // => [1]
   *
   * var food = [
   *   { 'name': 'beet',   'organic': false },
   *   { 'name': 'carrot', 'organic': true }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.initial(food, 'organic');
   * // => [{ 'name': 'beet',   'organic': false }]
   *
   * var food = [
   *   { 'name': 'banana', 'type': 'fruit' },
   *   { 'name': 'beet',   'type': 'vegetable' },
   *   { 'name': 'carrot', 'type': 'vegetable' }
   * ];
   *
   * // using "_.where" callback shorthand
   * _.initial(food, { 'type': 'vegetable' });
   * // => [{ 'name': 'banana', 'type': 'fruit' }]
   */
  function initial(array, callback, thisArg) {
    if (!array) {
      return [];
    }
    var n = 0,
        length = array.length;

    if (typeof callback != 'number' && callback != null) {
      var index = length;
      callback = createCallback(callback, thisArg);
      while (index-- && callback(array[index], index, array)) {
        n++;
      }
    } else {
      n = (callback == null || thisArg) ? 1 : callback || n;
    }
    return slice(array, 0, nativeMin(nativeMax(0, length - n), length));
  }

  /**
   * Computes the intersection of all the passed-in arrays using strict equality
   * for comparisons, i.e. `===`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} [array1, array2, ...] Arrays to process.
   * @returns {Array} Returns a new array of unique elements that are present
   *  in **all** of the arrays.
   * @example
   *
   * _.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);
   * // => [1, 2]
   */
  function intersection(array) {
    var args = arguments,
        argsLength = args.length,
        cache = { '0': {} },
        index = -1,
        length = array ? array.length : 0,
        isLarge = length >= 100,
        result = [],
        seen = result;

    outer:
    while (++index < length) {
      var value = array[index];
      if (isLarge) {
        var key = value + '';
        var inited = hasOwnProperty.call(cache[0], key)
          ? !(seen = cache[0][key])
          : (seen = cache[0][key] = []);
      }
      if (inited || indexOf(seen, value) < 0) {
        if (isLarge) {
          seen.push(value);
        }
        var argsIndex = argsLength;
        while (--argsIndex) {
          if (!(cache[argsIndex] || (cache[argsIndex] = cachedContains(args[argsIndex], 0, 100)))(value)) {
            continue outer;
          }
        }
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Gets the last element of the `array`. If a number `n` is passed, the last
   * `n` elements of the `array` are returned. If a `callback` function is passed,
   * the last elements the `callback` returns truthy for are returned. The `callback`
   * is bound to `thisArg` and invoked with three arguments; (value, index, array).
   *
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to query.
   * @param {Function|Object|Number|String} [callback|n] The function called
   *  per element or the number of elements to return. If a property name or
   *  object is passed, it will be used to create a "_.pluck" or "_.where"
   *  style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Mixed} Returns the last element(s) of `array`.
   * @example
   *
   * _.last([1, 2, 3]);
   * // => 3
   *
   * _.last([1, 2, 3], 2);
   * // => [2, 3]
   *
   * _.last([1, 2, 3], function(num) {
   *   return num > 1;
   * });
   * // => [2, 3]
   *
   * var food = [
   *   { 'name': 'beet',   'organic': false },
   *   { 'name': 'carrot', 'organic': true }
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.last(food, 'organic');
   * // => [{ 'name': 'carrot', 'organic': true }]
   *
   * var food = [
   *   { 'name': 'banana', 'type': 'fruit' },
   *   { 'name': 'beet',   'type': 'vegetable' },
   *   { 'name': 'carrot', 'type': 'vegetable' }
   * ];
   *
   * // using "_.where" callback shorthand
   * _.last(food, { 'type': 'vegetable' });
   * // => [{ 'name': 'beet', 'type': 'vegetable' }, { 'name': 'carrot', 'type': 'vegetable' }]
   */
  function last(array, callback, thisArg) {
    if (array) {
      var n = 0,
          length = array.length;

      if (typeof callback != 'number' && callback != null) {
        var index = length;
        callback = createCallback(callback, thisArg);
        while (index-- && callback(array[index], index, array)) {
          n++;
        }
      } else {
        n = callback;
        if (n == null || thisArg) {
          return array[length - 1];
        }
      }
      return slice(array, nativeMax(0, length - n));
    }
  }

  /**
   * Gets the index at which the last occurrence of `value` is found using strict
   * equality for comparisons, i.e. `===`. If `fromIndex` is negative, it is used
   * as the offset from the end of the collection.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to search.
   * @param {Mixed} value The value to search for.
   * @param {Number} [fromIndex=array.length-1] The index to search from.
   * @returns {Number} Returns the index of the matched value or `-1`.
   * @example
   *
   * _.lastIndexOf([1, 2, 3, 1, 2, 3], 2);
   * // => 4
   *
   * _.lastIndexOf([1, 2, 3, 1, 2, 3], 2, 3);
   * // => 1
   */
  function lastIndexOf(array, value, fromIndex) {
    var index = array ? array.length : 0;
    if (typeof fromIndex == 'number') {
      index = (fromIndex < 0 ? nativeMax(0, index + fromIndex) : nativeMin(fromIndex, index - 1)) + 1;
    }
    while (index--) {
      if (array[index] === value) {
        return index;
      }
    }
    return -1;
  }

  /**
   * Creates an object composed from arrays of `keys` and `values`. Pass either
   * a single two dimensional array, i.e. `[[key1, value1], [key2, value2]]`, or
   * two arrays, one of `keys` and one of corresponding `values`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} keys The array of keys.
   * @param {Array} [values=[]] The array of values.
   * @returns {Object} Returns an object composed of the given keys and
   *  corresponding values.
   * @example
   *
   * _.object(['moe', 'larry'], [30, 40]);
   * // => { 'moe': 30, 'larry': 40 }
   */
  function object(keys, values) {
    var index = -1,
        length = keys ? keys.length : 0,
        result = {};

    while (++index < length) {
      var key = keys[index];
      if (values) {
        result[key] = values[index];
      } else {
        result[key[0]] = key[1];
      }
    }
    return result;
  }

  /**
   * Creates an array of numbers (positive and/or negative) progressing from
   * `start` up to but not including `end`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Number} [start=0] The start of the range.
   * @param {Number} end The end of the range.
   * @param {Number} [step=1] The value to increment or descrement by.
   * @returns {Array} Returns a new range array.
   * @example
   *
   * _.range(10);
   * // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   *
   * _.range(1, 11);
   * // => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   *
   * _.range(0, 30, 5);
   * // => [0, 5, 10, 15, 20, 25]
   *
   * _.range(0, -10, -1);
   * // => [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
   *
   * _.range(0);
   * // => []
   */
  function range(start, end, step) {
    start = +start || 0;
    step = +step || 1;

    if (end == null) {
      end = start;
      start = 0;
    }
    // use `Array(length)` so V8 will avoid the slower "dictionary" mode
    // http://youtu.be/XAqIpGU8ZZk#t=17m25s
    var index = -1,
        length = nativeMax(0, ceil((end - start) / step)),
        result = Array(length);

    while (++index < length) {
      result[index] = start;
      start += step;
    }
    return result;
  }

  /**
   * The opposite of `_.initial`, this method gets all but the first value of `array`.
   * If a number `n` is passed, the first `n` values are excluded from the result.
   * If a `callback` function is passed, the first elements the `callback` returns
   * truthy for are excluded from the result. The `callback` is bound to `thisArg`
   * and invoked with three arguments; (value, index, array).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias drop, tail
   * @category Arrays
   * @param {Array} array The array to query.
   * @param {Function|Object|Number|String} [callback|n=1] The function called
   *  per element or the number of elements to exclude. If a property name or
   *  object is passed, it will be used to create a "_.pluck" or "_.where"
   *  style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a slice of `array`.
   * @example
   *
   * _.rest([1, 2, 3]);
   * // => [2, 3]
   *
   * _.rest([1, 2, 3], 2);
   * // => [3]
   *
   * _.rest([1, 2, 3], function(num) {
   *   return num < 3;
   * });
   * // => [3]
   *
   * var food = [
   *   { 'name': 'banana', 'organic': true },
   *   { 'name': 'beet',   'organic': false },
   * ];
   *
   * // using "_.pluck" callback shorthand
   * _.rest(food, 'organic');
   * // => [{ 'name': 'beet', 'organic': false }]
   *
   * var food = [
   *   { 'name': 'apple',  'type': 'fruit' },
   *   { 'name': 'banana', 'type': 'fruit' },
   *   { 'name': 'beet',   'type': 'vegetable' }
   * ];
   *
   * // using "_.where" callback shorthand
   * _.rest(food, { 'type': 'fruit' });
   * // => [{ 'name': 'beet', 'type': 'vegetable' }]
   */
  function rest(array, callback, thisArg) {
    if (typeof callback != 'number' && callback != null) {
      var n = 0,
          index = -1,
          length = array ? array.length : 0;

      callback = createCallback(callback, thisArg);
      while (++index < length && callback(array[index], index, array)) {
        n++;
      }
    } else {
      n = (callback == null || thisArg) ? 1 : nativeMax(0, callback);
    }
    return slice(array, n);
  }

  /**
   * Uses a binary search to determine the smallest index at which the `value`
   * should be inserted into `array` in order to maintain the sort order of the
   * sorted `array`. If `callback` is passed, it will be executed for `value` and
   * each element in `array` to compute their sort ranking. The `callback` is
   * bound to `thisArg` and invoked with one argument; (value).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to iterate over.
   * @param {Mixed} value The value to evaluate.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Number} Returns the index at which the value should be inserted
   *  into `array`.
   * @example
   *
   * _.sortedIndex([20, 30, 50], 40);
   * // => 2
   *
   * // using "_.pluck" callback shorthand
   * _.sortedIndex([{ 'x': 20 }, { 'x': 30 }, { 'x': 50 }], { 'x': 40 }, 'x');
   * // => 2
   *
   * var dict = {
   *   'wordToNumber': { 'twenty': 20, 'thirty': 30, 'fourty': 40, 'fifty': 50 }
   * };
   *
   * _.sortedIndex(['twenty', 'thirty', 'fifty'], 'fourty', function(word) {
   *   return dict.wordToNumber[word];
   * });
   * // => 2
   *
   * _.sortedIndex(['twenty', 'thirty', 'fifty'], 'fourty', function(word) {
   *   return this.wordToNumber[word];
   * }, dict);
   * // => 2
   */
  function sortedIndex(array, value, callback, thisArg) {
    var low = 0,
        high = array ? array.length : low;

    // explicitly reference `identity` for better inlining in Firefox
    callback = callback ? createCallback(callback, thisArg, 1) : identity;
    value = callback(value);

    while (low < high) {
      var mid = (low + high) >>> 1;
      callback(array[mid]) < value
        ? low = mid + 1
        : high = mid;
    }
    return low;
  }

  /**
   * Computes the union of the passed-in arrays using strict equality for
   * comparisons, i.e. `===`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} [array1, array2, ...] Arrays to process.
   * @returns {Array} Returns a new array of unique values, in order, that are
   *  present in one or more of the arrays.
   * @example
   *
   * _.union([1, 2, 3], [101, 2, 1, 10], [2, 1]);
   * // => [1, 2, 3, 101, 10]
   */
  function union() {
    return uniq(concat.apply(arrayRef, arguments));
  }

  /**
   * Creates a duplicate-value-free version of the `array` using strict equality
   * for comparisons, i.e. `===`. If the `array` is already sorted, passing `true`
   * for `isSorted` will run a faster algorithm. If `callback` is passed, each
   * element of `array` is passed through a callback` before uniqueness is computed.
   * The `callback` is bound to `thisArg` and invoked with three arguments; (value, index, array).
   *
   * If a property name is passed for `callback`, the created "_.pluck" style
   * callback will return the property value of the given element.
   *
   * If an object is passed for `callback`, the created "_.where" style callback
   * will return `true` for elements that have the propeties of the given object,
   * else `false`.
   *
   * @static
   * @memberOf _
   * @alias unique
   * @category Arrays
   * @param {Array} array The array to process.
   * @param {Boolean} [isSorted=false] A flag to indicate that the `array` is already sorted.
   * @param {Function|Object|String} [callback=identity] The function called per
   *  iteration. If a property name or object is passed, it will be used to create
   *  a "_.pluck" or "_.where" style callback, respectively.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a duplicate-value-free array.
   * @example
   *
   * _.uniq([1, 2, 1, 3, 1]);
   * // => [1, 2, 3]
   *
   * _.uniq([1, 1, 2, 2, 3], true);
   * // => [1, 2, 3]
   *
   * _.uniq([1, 2, 1.5, 3, 2.5], function(num) { return Math.floor(num); });
   * // => [1, 2, 3]
   *
   * _.uniq([1, 2, 1.5, 3, 2.5], function(num) { return this.floor(num); }, Math);
   * // => [1, 2, 3]
   *
   * // using "_.pluck" callback shorthand
   * _.uniq([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
   * // => [{ 'x': 1 }, { 'x': 2 }]
   */
  function uniq(array, isSorted, callback, thisArg) {
    var index = -1,
        length = array ? array.length : 0,
        result = [],
        seen = result;

    // juggle arguments
    if (typeof isSorted == 'function') {
      thisArg = callback;
      callback = isSorted;
      isSorted = false;
    }
    // init value cache for large arrays
    var isLarge = !isSorted && length >= 75;
    if (isLarge) {
      var cache = {};
    }
    if (callback) {
      seen = [];
      callback = createCallback(callback, thisArg);
    }
    while (++index < length) {
      var value = array[index],
          computed = callback ? callback(value, index, array) : value;

      if (isLarge) {
        var key = computed + '';
        var inited = hasOwnProperty.call(cache, key)
          ? !(seen = cache[key])
          : (seen = cache[key] = []);
      }
      if (isSorted
            ? !index || seen[seen.length - 1] !== computed
            : inited || indexOf(seen, computed) < 0
          ) {
        if (callback || isLarge) {
          seen.push(computed);
        }
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Creates an array with all occurrences of the passed values removed using
   * strict equality for comparisons, i.e. `===`.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} array The array to filter.
   * @param {Mixed} [value1, value2, ...] Values to remove.
   * @returns {Array} Returns a new filtered array.
   * @example
   *
   * _.without([1, 2, 1, 0, 3, 1, 4], 0, 1);
   * // => [2, 3, 4]
   */
  function without(array) {
    var index = -1,
        length = array ? array.length : 0,
        contains = cachedContains(arguments, 1),
        result = [];

    while (++index < length) {
      var value = array[index];
      if (!contains(value)) {
        result.push(value);
      }
    }
    return result;
  }

  /**
   * Groups the elements of each array at their corresponding indexes. Useful for
   * separate data sources that are coordinated through matching array indexes.
   * For a matrix of nested arrays, `_.zip.apply(...)` can transpose the matrix
   * in a similar fashion.
   *
   * @static
   * @memberOf _
   * @category Arrays
   * @param {Array} [array1, array2, ...] Arrays to process.
   * @returns {Array} Returns a new array of grouped elements.
   * @example
   *
   * _.zip(['moe', 'larry'], [30, 40], [true, false]);
   * // => [['moe', 30, true], ['larry', 40, false]]
   */
  function zip(array) {
    var index = -1,
        length = array ? max(pluck(arguments, 'length')) : 0,
        result = Array(length);

    while (++index < length) {
      result[index] = pluck(arguments, index);
    }
    return result;
  }

  /*--------------------------------------------------------------------------*/

  /**
   * Creates a function that is restricted to executing `func` only after it is
   * called `n` times. The `func` is executed with the `this` binding of the
   * created function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Number} n The number of times the function must be called before
   * it is executed.
   * @param {Function} func The function to restrict.
   * @returns {Function} Returns the new restricted function.
   * @example
   *
   * var renderNotes = _.after(notes.length, render);
   * _.forEach(notes, function(note) {
   *   note.asyncSave({ 'success': renderNotes });
   * });
   * // `renderNotes` is run once, after all notes have saved
   */
  function after(n, func) {
    if (n < 1) {
      return func();
    }
    return function() {
      if (--n < 1) {
        return func.apply(this, arguments);
      }
    };
  }

  /**
   * Creates a function that, when called, invokes `func` with the `this`
   * binding of `thisArg` and prepends any additional `bind` arguments to those
   * passed to the bound function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to bind.
   * @param {Mixed} [thisArg] The `this` binding of `func`.
   * @param {Mixed} [arg1, arg2, ...] Arguments to be partially applied.
   * @returns {Function} Returns the new bound function.
   * @example
   *
   * var func = function(greeting) {
   *   return greeting + ' ' + this.name;
   * };
   *
   * func = _.bind(func, { 'name': 'moe' }, 'hi');
   * func();
   * // => 'hi moe'
   */
  function bind(func, thisArg) {
    // use `Function#bind` if it exists and is fast
    // (in V8 `Function#bind` is slower except when partially applied)
    return isBindFast || (nativeBind && arguments.length > 2)
      ? nativeBind.call.apply(nativeBind, arguments)
      : createBound(func, thisArg, slice(arguments, 2));
  }

  /**
   * Binds methods on `object` to `object`, overwriting the existing method.
   * Method names may be specified as individual arguments or as arrays of method
   * names. If no method names are provided, all the function properties of `object`
   * will be bound.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Object} object The object to bind and assign the bound methods to.
   * @param {String} [methodName1, methodName2, ...] Method names on the object to bind.
   * @returns {Object} Returns `object`.
   * @example
   *
   * var view = {
   *  'label': 'docs',
   *  'onClick': function() { alert('clicked ' + this.label); }
   * };
   *
   * _.bindAll(view);
   * jQuery('#docs').on('click', view.onClick);
   * // => alerts 'clicked docs', when the button is clicked
   */
  function bindAll(object) {
    var funcs = concat.apply(arrayRef, arguments),
        index = funcs.length > 1 ? 0 : (funcs = functions(object), -1),
        length = funcs.length;

    while (++index < length) {
      var key = funcs[index];
      object[key] = bind(object[key], object);
    }
    return object;
  }

  /**
   * Creates a function that, when called, invokes the method at `object[key]`
   * and prepends any additional `bindKey` arguments to those passed to the bound
   * function. This method differs from `_.bind` by allowing bound functions to
   * reference methods that will be redefined or don't yet exist.
   * See http://michaux.ca/articles/lazy-function-definition-pattern.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Object} object The object the method belongs to.
   * @param {String} key The key of the method.
   * @param {Mixed} [arg1, arg2, ...] Arguments to be partially applied.
   * @returns {Function} Returns the new bound function.
   * @example
   *
   * var object = {
   *   'name': 'moe',
   *   'greet': function(greeting) {
   *     return greeting + ' ' + this.name;
   *   }
   * };
   *
   * var func = _.bindKey(object, 'greet', 'hi');
   * func();
   * // => 'hi moe'
   *
   * object.greet = function(greeting) {
   *   return greeting + ', ' + this.name + '!';
   * };
   *
   * func();
   * // => 'hi, moe!'
   */
  function bindKey(object, key) {
    return createBound(object, key, slice(arguments, 2));
  }

  /**
   * Creates a function that is the composition of the passed functions,
   * where each function consumes the return value of the function that follows.
   * For example, composing the functions `f()`, `g()`, and `h()` produces `f(g(h()))`.
   * Each function is executed with the `this` binding of the composed function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} [func1, func2, ...] Functions to compose.
   * @returns {Function} Returns the new composed function.
   * @example
   *
   * var greet = function(name) { return 'hi ' + name; };
   * var exclaim = function(statement) { return statement + '!'; };
   * var welcome = _.compose(exclaim, greet);
   * welcome('moe');
   * // => 'hi moe!'
   */
  function compose() {
    var funcs = arguments;
    return function() {
      var args = arguments,
          length = funcs.length;

      while (length--) {
        args = [funcs[length].apply(this, args)];
      }
      return args[0];
    };
  }

  /**
   * Creates a function that will delay the execution of `func` until after
   * `wait` milliseconds have elapsed since the last time it was invoked. Pass
   * `true` for `immediate` to cause debounce to invoke `func` on the leading,
   * instead of the trailing, edge of the `wait` timeout. Subsequent calls to
   * the debounced function will return the result of the last `func` call.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to debounce.
   * @param {Number} wait The number of milliseconds to delay.
   * @param {Boolean} immediate A flag to indicate execution is on the leading
   *  edge of the timeout.
   * @returns {Function} Returns the new debounced function.
   * @example
   *
   * var lazyLayout = _.debounce(calculateLayout, 300);
   * jQuery(window).on('resize', lazyLayout);
   */
  function debounce(func, wait, immediate) {
    var args,
        result,
        thisArg,
        timeoutId;

    function delayed() {
      timeoutId = null;
      if (!immediate) {
        result = func.apply(thisArg, args);
      }
    }
    return function() {
      var isImmediate = immediate && !timeoutId;
      args = arguments;
      thisArg = this;

      clearTimeout(timeoutId);
      timeoutId = setTimeout(delayed, wait);

      if (isImmediate) {
        result = func.apply(thisArg, args);
      }
      return result;
    };
  }

  /**
   * Executes the `func` function after `wait` milliseconds. Additional arguments
   * will be passed to `func` when it is invoked.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to delay.
   * @param {Number} wait The number of milliseconds to delay execution.
   * @param {Mixed} [arg1, arg2, ...] Arguments to invoke the function with.
   * @returns {Number} Returns the `setTimeout` timeout id.
   * @example
   *
   * var log = _.bind(console.log, console);
   * _.delay(log, 1000, 'logged later');
   * // => 'logged later' (Appears after one second.)
   */
  function delay(func, wait) {
    var args = slice(arguments, 2);
    return setTimeout(function() { func.apply(undefined, args); }, wait);
  }

  /**
   * Defers executing the `func` function until the current call stack has cleared.
   * Additional arguments will be passed to `func` when it is invoked.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to defer.
   * @param {Mixed} [arg1, arg2, ...] Arguments to invoke the function with.
   * @returns {Number} Returns the `setTimeout` timeout id.
   * @example
   *
   * _.defer(function() { alert('deferred'); });
   * // returns from the function before `alert` is called
   */
  function defer(func) {
    var args = slice(arguments, 1);
    return setTimeout(function() { func.apply(undefined, args); }, 1);
  }
  // use `setImmediate` if it's available in Node.js
  if (isV8 && freeModule && typeof setImmediate == 'function') {
    defer = bind(setImmediate, window);
  }

  /**
   * Creates a function that memoizes the result of `func`. If `resolver` is
   * passed, it will be used to determine the cache key for storing the result
   * based on the arguments passed to the memoized function. By default, the first
   * argument passed to the memoized function is used as the cache key. The `func`
   * is executed with the `this` binding of the memoized function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to have its output memoized.
   * @param {Function} [resolver] A function used to resolve the cache key.
   * @returns {Function} Returns the new memoizing function.
   * @example
   *
   * var fibonacci = _.memoize(function(n) {
   *   return n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2);
   * });
   */
  function memoize(func, resolver) {
    var cache = {};
    return function() {
      var key = (resolver ? resolver.apply(this, arguments) : arguments[0]) + '';
      return hasOwnProperty.call(cache, key)
        ? cache[key]
        : (cache[key] = func.apply(this, arguments));
    };
  }

  /**
   * Creates a function that is restricted to execute `func` once. Repeat calls to
   * the function will return the value of the first call. The `func` is executed
   * with the `this` binding of the created function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to restrict.
   * @returns {Function} Returns the new restricted function.
   * @example
   *
   * var initialize = _.once(createApplication);
   * initialize();
   * initialize();
   * // `initialize` executes `createApplication` once
   */
  function once(func) {
    var ran,
        result;

    return function() {
      if (ran) {
        return result;
      }
      ran = true;
      result = func.apply(this, arguments);

      // clear the `func` variable so the function may be garbage collected
      func = null;
      return result;
    };
  }

  /**
   * Creates a function that, when called, invokes `func` with any additional
   * `partial` arguments prepended to those passed to the new function. This
   * method is similar to `_.bind`, except it does **not** alter the `this` binding.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to partially apply arguments to.
   * @param {Mixed} [arg1, arg2, ...] Arguments to be partially applied.
   * @returns {Function} Returns the new partially applied function.
   * @example
   *
   * var greet = function(greeting, name) { return greeting + ' ' + name; };
   * var hi = _.partial(greet, 'hi');
   * hi('moe');
   * // => 'hi moe'
   */
  function partial(func) {
    return createBound(func, slice(arguments, 1));
  }

  /**
   * This method is similar to `_.partial`, except that `partial` arguments are
   * appended to those passed to the new function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to partially apply arguments to.
   * @param {Mixed} [arg1, arg2, ...] Arguments to be partially applied.
   * @returns {Function} Returns the new partially applied function.
   * @example
   *
   * var defaultsDeep = _.partialRight(_.merge, _.defaults);
   *
   * var options = {
   *   'variable': 'data',
   *   'imports': { 'jq': $ }
   * };
   *
   * defaultsDeep(options, _.templateSettings);
   *
   * options.variable
   * // => 'data'
   *
   * options.imports
   * // => { '_': _, 'jq': $ }
   */
  function partialRight(func) {
    return createBound(func, slice(arguments, 1), null, indicatorObject);
  }

  /**
   * Creates a function that, when executed, will only call the `func`
   * function at most once per every `wait` milliseconds. If the throttled
   * function is invoked more than once during the `wait` timeout, `func` will
   * also be called on the trailing edge of the timeout. Subsequent calls to the
   * throttled function will return the result of the last `func` call.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Function} func The function to throttle.
   * @param {Number} wait The number of milliseconds to throttle executions to.
   * @returns {Function} Returns the new throttled function.
   * @example
   *
   * var throttled = _.throttle(updatePosition, 100);
   * jQuery(window).on('scroll', throttled);
   */
  function throttle(func, wait) {
    var args,
        result,
        thisArg,
        timeoutId,
        lastCalled = 0;

    function trailingCall() {
      lastCalled = new Date;
      timeoutId = null;
      result = func.apply(thisArg, args);
    }
    return function() {
      var now = new Date,
          remaining = wait - (now - lastCalled);

      args = arguments;
      thisArg = this;

      if (remaining <= 0) {
        clearTimeout(timeoutId);
        timeoutId = null;
        lastCalled = now;
        result = func.apply(thisArg, args);
      }
      else if (!timeoutId) {
        timeoutId = setTimeout(trailingCall, remaining);
      }
      return result;
    };
  }

  /**
   * Creates a function that passes `value` to the `wrapper` function as its
   * first argument. Additional arguments passed to the function are appended
   * to those passed to the `wrapper` function. The `wrapper` is executed with
   * the `this` binding of the created function.
   *
   * @static
   * @memberOf _
   * @category Functions
   * @param {Mixed} value The value to wrap.
   * @param {Function} wrapper The wrapper function.
   * @returns {Function} Returns the new function.
   * @example
   *
   * var hello = function(name) { return 'hello ' + name; };
   * hello = _.wrap(hello, function(func) {
   *   return 'before, ' + func('moe') + ', after';
   * });
   * hello();
   * // => 'before, hello moe, after'
   */
  function wrap(value, wrapper) {
    return function() {
      var args = [value];
      push.apply(args, arguments);
      return wrapper.apply(this, args);
    };
  }

  /*--------------------------------------------------------------------------*/

  /**
   * Converts the characters `&`, `<`, `>`, `"`, and `'` in `string` to their
   * corresponding HTML entities.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {String} string The string to escape.
   * @returns {String} Returns the escaped string.
   * @example
   *
   * _.escape('Moe, Larry & Curly');
   * // => 'Moe, Larry &amp; Curly'
   */
  function escape(string) {
    return string == null ? '' : (string + '').replace(reUnescapedHtml, escapeHtmlChar);
  }

  /**
   * This function returns the first argument passed to it.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {Mixed} value Any value.
   * @returns {Mixed} Returns `value`.
   * @example
   *
   * var moe = { 'name': 'moe' };
   * moe === _.identity(moe);
   * // => true
   */
  function identity(value) {
    return value;
  }

  /**
   * Adds functions properties of `object` to the `lodash` function and chainable
   * wrapper.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {Object} object The object of function properties to add to `lodash`.
   * @example
   *
   * _.mixin({
   *   'capitalize': function(string) {
   *     return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
   *   }
   * });
   *
   * _.capitalize('moe');
   * // => 'Moe'
   *
   * _('moe').capitalize();
   * // => 'Moe'
   */
  function mixin(object) {
    forEach(functions(object), function(methodName) {
      var func = lodash[methodName] = object[methodName];

      lodash.prototype[methodName] = function() {
        var args = [this.__wrapped__];
        push.apply(args, arguments);
        return new lodash(func.apply(lodash, args));
      };
    });
  }

  /**
   * Reverts the '_' variable to its previous value and returns a reference to
   * the `lodash` function.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @returns {Function} Returns the `lodash` function.
   * @example
   *
   * var lodash = _.noConflict();
   */
  function noConflict() {
    window._ = oldDash;
    return this;
  }

  /**
   * Produces a random number between `min` and `max` (inclusive). If only one
   * argument is passed, a number between `0` and the given number will be returned.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {Number} [min=0] The minimum possible value.
   * @param {Number} [max=1] The maximum possible value.
   * @returns {Number} Returns a random number.
   * @example
   *
   * _.random(0, 5);
   * // => a number between 0 and 5
   *
   * _.random(5);
   * // => also a number between 0 and 5
   */
  function random(min, max) {
    if (min == null && max == null) {
      max = 1;
    }
    min = +min || 0;
    if (max == null) {
      max = min;
      min = 0;
    }
    return min + floor(nativeRandom() * ((+max || 0) - min + 1));
  }

  /**
   * Resolves the value of `property` on `object`. If `property` is a function,
   * it will be invoked and its result returned, else the property value is
   * returned. If `object` is falsey, then `null` is returned.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {Object} object The object to inspect.
   * @param {String} property The property to get the value of.
   * @returns {Mixed} Returns the resolved value.
   * @example
   *
   * var object = {
   *   'cheese': 'crumpets',
   *   'stuff': function() {
   *     return 'nonsense';
   *   }
   * };
   *
   * _.result(object, 'cheese');
   * // => 'crumpets'
   *
   * _.result(object, 'stuff');
   * // => 'nonsense'
   */
  function result(object, property) {
    var value = object ? object[property] : undefined;
    return isFunction(value) ? object[property]() : value;
  }

  /**
   * A micro-templating method that handles arbitrary delimiters, preserves
   * whitespace, and correctly escapes quotes within interpolated code.
   *
   * Note: In the development build, `_.template` utilizes sourceURLs for easier
   * debugging. See http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl
   *
   * Note: Lo-Dash may be used in Chrome extensions by either creating a `lodash csp`
   * build and using precompiled templates, or loading Lo-Dash in a sandbox.
   *
   * For more information on precompiling templates see:
   * http://lodash.com/#custom-builds
   *
   * For more information on Chrome extension sandboxes see:
   * http://developer.chrome.com/stable/extensions/sandboxingEval.html
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {String} text The template text.
   * @param {Obect} data The data object used to populate the text.
   * @param {Object} options The options object.
   *  escape - The "escape" delimiter regexp.
   *  evaluate - The "evaluate" delimiter regexp.
   *  interpolate - The "interpolate" delimiter regexp.
   *  sourceURL - The sourceURL of the template's compiled source.
   *  variable - The data object variable name.
   *
   * @returns {Function|String} Returns a compiled function when no `data` object
   *  is given, else it returns the interpolated text.
   * @example
   *
   * // using a compiled template
   * var compiled = _.template('hello <%= name %>');
   * compiled({ 'name': 'moe' });
   * // => 'hello moe'
   *
   * var list = '<% _.forEach(people, function(name) { %><li><%= name %></li><% }); %>';
   * _.template(list, { 'people': ['moe', 'larry'] });
   * // => '<li>moe</li><li>larry</li>'
   *
   * // using the "escape" delimiter to escape HTML in data property values
   * _.template('<b><%- value %></b>', { 'value': '<script>' });
   * // => '<b>&lt;script&gt;</b>'
   *
   * // using the ES6 delimiter as an alternative to the default "interpolate" delimiter
   * _.template('hello ${ name }', { 'name': 'curly' });
   * // => 'hello curly'
   *
   * // using the internal `print` function in "evaluate" delimiters
   * _.template('<% print("hello " + epithet); %>!', { 'epithet': 'stooge' });
   * // => 'hello stooge!'
   *
   * // using custom template delimiters
   * _.templateSettings = {
   *   'interpolate': /{{([\s\S]+?)}}/g
   * };
   *
   * _.template('hello {{ name }}!', { 'name': 'mustache' });
   * // => 'hello mustache!'
   *
   * // using the `sourceURL` option to specify a custom sourceURL for the template
   * var compiled = _.template('hello <%= name %>', null, { 'sourceURL': '/basic/greeting.jst' });
   * compiled(data);
   * // => find the source of "greeting.jst" under the Sources tab or Resources panel of the web inspector
   *
   * // using the `variable` option to ensure a with-statement isn't used in the compiled template
   * var compiled = _.template('hi <%= data.name %>!', null, { 'variable': 'data' });
   * compiled.source;
   * // => function(data) {
   *   var __t, __p = '', __e = _.escape;
   *   __p += 'hi ' + ((__t = ( data.name )) == null ? '' : __t) + '!';
   *   return __p;
   * }
   *
   * // using the `source` property to inline compiled templates for meaningful
   * // line numbers in error messages and a stack trace
   * fs.writeFileSync(path.join(cwd, 'jst.js'), '\
   *   var JST = {\
   *     "main": ' + _.template(mainText).source + '\
   *   };\
   * ');
   */
  function template(text, data, options) {
    // based on John Resig's `tmpl` implementation
    // http://ejohn.org/blog/javascript-micro-templating/
    // and Laura Doktorova's doT.js
    // https://github.com/olado/doT
    var settings = lodash.templateSettings;
    text || (text = '');

    // avoid missing dependencies when `iteratorTemplate` is not defined
    options = defaults({}, options, settings);

    var imports = defaults({}, options.imports, settings.imports),
        importsKeys = keys(imports),
        importsValues = values(imports);

    var isEvaluating,
        index = 0,
        interpolate = options.interpolate || reNoMatch,
        source = "__p += '";

    // compile regexp to match each delimiter
    var reDelimiters = RegExp(
      (options.escape || reNoMatch).source + '|' +
      interpolate.source + '|' +
      (interpolate === reInterpolate ? reEsTemplate : reNoMatch).source + '|' +
      (options.evaluate || reNoMatch).source + '|$'
    , 'g');

    text.replace(reDelimiters, function(match, escapeValue, interpolateValue, esTemplateValue, evaluateValue, offset) {
      interpolateValue || (interpolateValue = esTemplateValue);

      // escape characters that cannot be included in string literals
      source += text.slice(index, offset).replace(reUnescapedString, escapeStringChar);

      // replace delimiters with snippets
      if (escapeValue) {
        source += "' +\n__e(" + escapeValue + ") +\n'";
      }
      if (evaluateValue) {
        isEvaluating = true;
        source += "';\n" + evaluateValue + ";\n__p += '";
      }
      if (interpolateValue) {
        source += "' +\n((__t = (" + interpolateValue + ")) == null ? '' : __t) +\n'";
      }
      index = offset + match.length;

      // the JS engine embedded in Adobe products requires returning the `match`
      // string in order to produce the correct `offset` value
      return match;
    });

    source += "';\n";

    // if `variable` is not specified and the template contains "evaluate"
    // delimiters, wrap a with-statement around the generated code to add the
    // data object to the top of the scope chain
    var variable = options.variable,
        hasVariable = variable;

    if (!hasVariable) {
      variable = 'obj';
      source = 'with (' + variable + ') {\n' + source + '\n}\n';
    }
    // cleanup code by stripping empty strings
    source = (isEvaluating ? source.replace(reEmptyStringLeading, '') : source)
      .replace(reEmptyStringMiddle, '$1')
      .replace(reEmptyStringTrailing, '$1;');

    // frame code as the function body
    source = 'function(' + variable + ') {\n' +
      (hasVariable ? '' : variable + ' || (' + variable + ' = {});\n') +
      "var __t, __p = '', __e = _.escape" +
      (isEvaluating
        ? ', __j = Array.prototype.join;\n' +
          "function print() { __p += __j.call(arguments, '') }\n"
        : ';\n'
      ) +
      source +
      'return __p\n}';

    // Use a sourceURL for easier debugging and wrap in a multi-line comment to
    // avoid issues with Narwhal, IE conditional compilation, and the JS engine
    // embedded in Adobe products.
    // http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl
    var sourceURL = '\n/*\n//@ sourceURL=' + (options.sourceURL || '/lodash/template/source[' + (templateCounter++) + ']') + '\n*/';

    try {
      var result = Function(importsKeys, 'return ' + source + sourceURL).apply(undefined, importsValues);
    } catch(e) {
      e.source = source;
      throw e;
    }
    if (data) {
      return result(data);
    }
    // provide the compiled function's source via its `toString` method, in
    // supported environments, or the `source` property as a convenience for
    // inlining compiled templates during the build process
    result.source = source;
    return result;
  }

  /**
   * Executes the `callback` function `n` times, returning an array of the results
   * of each `callback` execution. The `callback` is bound to `thisArg` and invoked
   * with one argument; (index).
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {Number} n The number of times to execute the callback.
   * @param {Function} callback The function called per iteration.
   * @param {Mixed} [thisArg] The `this` binding of `callback`.
   * @returns {Array} Returns a new array of the results of each `callback` execution.
   * @example
   *
   * var diceRolls = _.times(3, _.partial(_.random, 1, 6));
   * // => [3, 6, 4]
   *
   * _.times(3, function(n) { mage.castSpell(n); });
   * // => calls `mage.castSpell(n)` three times, passing `n` of `0`, `1`, and `2` respectively
   *
   * _.times(3, function(n) { this.cast(n); }, mage);
   * // => also calls `mage.castSpell(n)` three times
   */
  function times(n, callback, thisArg) {
    n = +n || 0;
    var index = -1,
        result = Array(n);

    while (++index < n) {
      result[index] = callback.call(thisArg, index);
    }
    return result;
  }

  /**
   * The opposite of `_.escape`, this method converts the HTML entities
   * `&amp;`, `&lt;`, `&gt;`, `&quot;`, and `&#39;` in `string` to their
   * corresponding characters.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {String} string The string to unescape.
   * @returns {String} Returns the unescaped string.
   * @example
   *
   * _.unescape('Moe, Larry &amp; Curly');
   * // => 'Moe, Larry & Curly'
   */
  function unescape(string) {
    return string == null ? '' : (string + '').replace(reEscapedHtml, unescapeHtmlChar);
  }

  /**
   * Generates a unique ID. If `prefix` is passed, the ID will be appended to it.
   *
   * @static
   * @memberOf _
   * @category Utilities
   * @param {String} [prefix] The value to prefix the ID with.
   * @returns {String} Returns the unique ID.
   * @example
   *
   * _.uniqueId('contact_');
   * // => 'contact_104'
   *
   * _.uniqueId();
   * // => '105'
   */
  function uniqueId(prefix) {
    var id = ++idCounter;
    return (prefix == null ? '' : prefix + '') + id;
  }

  /*--------------------------------------------------------------------------*/

  /**
   * Invokes `interceptor` with the `value` as the first argument, and then
   * returns `value`. The purpose of this method is to "tap into" a method chain,
   * in order to perform operations on intermediate results within the chain.
   *
   * @static
   * @memberOf _
   * @category Chaining
   * @param {Mixed} value The value to pass to `interceptor`.
   * @param {Function} interceptor The function to invoke.
   * @returns {Mixed} Returns `value`.
   * @example
   *
   * _([1, 2, 3, 4])
   *  .filter(function(num) { return num % 2 == 0; })
   *  .tap(alert)
   *  .map(function(num) { return num * num; })
   *  .value();
   * // => // [2, 4] (alerted)
   * // => [4, 16]
   */
  function tap(value, interceptor) {
    interceptor(value);
    return value;
  }

  /**
   * Produces the `toString` result of the wrapped value.
   *
   * @name toString
   * @memberOf _
   * @category Chaining
   * @returns {String} Returns the string result.
   * @example
   *
   * _([1, 2, 3]).toString();
   * // => '1,2,3'
   */
  function wrapperToString() {
    return this.__wrapped__ + '';
  }

  /**
   * Extracts the wrapped value.
   *
   * @name valueOf
   * @memberOf _
   * @alias value
   * @category Chaining
   * @returns {Mixed} Returns the wrapped value.
   * @example
   *
   * _([1, 2, 3]).valueOf();
   * // => [1, 2, 3]
   */
  function wrapperValueOf() {
    return this.__wrapped__;
  }

  /*--------------------------------------------------------------------------*/

  // add functions that return wrapped values when chaining
  lodash.after = after;
  lodash.assign = assign;
  lodash.at = at;
  lodash.bind = bind;
  lodash.bindAll = bindAll;
  lodash.bindKey = bindKey;
  lodash.compact = compact;
  lodash.compose = compose;
  lodash.countBy = countBy;
  lodash.debounce = debounce;
  lodash.defaults = defaults;
  lodash.defer = defer;
  lodash.delay = delay;
  lodash.difference = difference;
  lodash.filter = filter;
  lodash.flatten = flatten;
  lodash.forEach = forEach;
  lodash.forIn = forIn;
  lodash.forOwn = forOwn;
  lodash.functions = functions;
  lodash.groupBy = groupBy;
  lodash.initial = initial;
  lodash.intersection = intersection;
  lodash.invert = invert;
  lodash.invoke = invoke;
  lodash.keys = keys;
  lodash.map = map;
  lodash.max = max;
  lodash.memoize = memoize;
  lodash.merge = merge;
  lodash.min = min;
  lodash.object = object;
  lodash.omit = omit;
  lodash.once = once;
  lodash.pairs = pairs;
  lodash.partial = partial;
  lodash.partialRight = partialRight;
  lodash.pick = pick;
  lodash.pluck = pluck;
  lodash.range = range;
  lodash.reject = reject;
  lodash.rest = rest;
  lodash.shuffle = shuffle;
  lodash.sortBy = sortBy;
  lodash.tap = tap;
  lodash.throttle = throttle;
  lodash.times = times;
  lodash.toArray = toArray;
  lodash.union = union;
  lodash.uniq = uniq;
  lodash.values = values;
  lodash.where = where;
  lodash.without = without;
  lodash.wrap = wrap;
  lodash.zip = zip;

  // add aliases
  lodash.collect = map;
  lodash.drop = rest;
  lodash.each = forEach;
  lodash.extend = assign;
  lodash.methods = functions;
  lodash.select = filter;
  lodash.tail = rest;
  lodash.unique = uniq;

  // add functions to `lodash.prototype`
  mixin(lodash);

  /*--------------------------------------------------------------------------*/

  // add functions that return unwrapped values when chaining
  lodash.clone = clone;
  lodash.cloneDeep = cloneDeep;
  lodash.contains = contains;
  lodash.escape = escape;
  lodash.every = every;
  lodash.find = find;
  lodash.has = has;
  lodash.identity = identity;
  lodash.indexOf = indexOf;
  lodash.isArguments = isArguments;
  lodash.isArray = isArray;
  lodash.isBoolean = isBoolean;
  lodash.isDate = isDate;
  lodash.isElement = isElement;
  lodash.isEmpty = isEmpty;
  lodash.isEqual = isEqual;
  lodash.isFinite = isFinite;
  lodash.isFunction = isFunction;
  lodash.isNaN = isNaN;
  lodash.isNull = isNull;
  lodash.isNumber = isNumber;
  lodash.isObject = isObject;
  lodash.isPlainObject = isPlainObject;
  lodash.isRegExp = isRegExp;
  lodash.isString = isString;
  lodash.isUndefined = isUndefined;
  lodash.lastIndexOf = lastIndexOf;
  lodash.mixin = mixin;
  lodash.noConflict = noConflict;
  lodash.random = random;
  lodash.reduce = reduce;
  lodash.reduceRight = reduceRight;
  lodash.result = result;
  lodash.size = size;
  lodash.some = some;
  lodash.sortedIndex = sortedIndex;
  lodash.template = template;
  lodash.unescape = unescape;
  lodash.uniqueId = uniqueId;

  // add aliases
  lodash.all = every;
  lodash.any = some;
  lodash.detect = find;
  lodash.foldl = reduce;
  lodash.foldr = reduceRight;
  lodash.include = contains;
  lodash.inject = reduce;

  forOwn(lodash, function(func, methodName) {
    if (!lodash.prototype[methodName]) {
      lodash.prototype[methodName] = function() {
        var args = [this.__wrapped__];
        push.apply(args, arguments);
        return func.apply(lodash, args);
      };
    }
  });

  /*--------------------------------------------------------------------------*/

  // add functions capable of returning wrapped and unwrapped values when chaining
  lodash.first = first;
  lodash.last = last;

  // add aliases
  lodash.take = first;
  lodash.head = first;

  forOwn(lodash, function(func, methodName) {
    if (!lodash.prototype[methodName]) {
      lodash.prototype[methodName]= function(callback, thisArg) {
        var result = func(this.__wrapped__, callback, thisArg);
        return callback == null || (thisArg && typeof callback != 'function')
          ? result
          : new lodash(result);
      };
    }
  });

  /*--------------------------------------------------------------------------*/

  /**
   * The semantic version number.
   *
   * @static
   * @memberOf _
   * @type String
   */
  lodash.VERSION = '1.0.2';

  // add "Chaining" functions to the wrapper
  lodash.prototype.toString = wrapperToString;
  lodash.prototype.value = wrapperValueOf;
  lodash.prototype.valueOf = wrapperValueOf;

  // add `Array` functions that return unwrapped values
  each(['join', 'pop', 'shift'], function(methodName) {
    var func = arrayRef[methodName];
    lodash.prototype[methodName] = function() {
      return func.apply(this.__wrapped__, arguments);
    };
  });

  // add `Array` functions that return the wrapped value
  each(['push', 'reverse', 'sort', 'unshift'], function(methodName) {
    var func = arrayRef[methodName];
    lodash.prototype[methodName] = function() {
      func.apply(this.__wrapped__, arguments);
      return this;
    };
  });

  // add `Array` functions that return new wrapped values
  each(['concat', 'slice', 'splice'], function(methodName) {
    var func = arrayRef[methodName];
    lodash.prototype[methodName] = function() {
      return new lodash(func.apply(this.__wrapped__, arguments));
    };
  });

  // avoid array-like object bugs with `Array#shift` and `Array#splice`
  // in Firefox < 10 and IE < 9
  if (hasObjectSpliceBug) {
    each(['pop', 'shift', 'splice'], function(methodName) {
      var func = arrayRef[methodName],
          isSplice = methodName == 'splice';

      lodash.prototype[methodName] = function() {
        var value = this.__wrapped__,
            result = func.apply(value, arguments);

        if (value.length === 0) {
          delete value[0];
        }
        return isSplice ? new lodash(result) : result;
      };
    });
  }

  /*--------------------------------------------------------------------------*/

  // expose Lo-Dash
  // some AMD build optimizers, like r.js, check for specific condition patterns like the following:
  if (typeof define == 'function' && typeof define.amd == 'object' && define.amd) {
    // Expose Lo-Dash to the global object even when an AMD loader is present in
    // case Lo-Dash was injected by a third-party script and not intended to be
    // loaded as a module. The global assignment can be reverted in the Lo-Dash
    // module via its `noConflict()` method.
    window._ = lodash;

    // define as an anonymous module so, through path mapping, it can be
    // referenced as the "underscore" module
    define(function() {
      return lodash;
    });
  }
  // check for `exports` after `define` in case a build optimizer adds an `exports` object
  else if (freeExports) {
    // in Node.js or RingoJS v0.8.0+
    if (freeModule) {
      (freeModule.exports = lodash)._ = lodash;
    }
    // in Narwhal or RingoJS v0.7.0-
    else {
      freeExports._ = lodash;
    }
  }
  else {
    // in a browser or Rhino
    window._ = lodash;
  }
}(this));