function map(collection, callback, thisArg) {
      var index = -1,
          length = collection ? collection.length : 0,
          result = Array(typeof length == 'number' ? length : 0);

      callback = lodash.createCallback(callback, thisArg, 3);
      if (isArray(collection)) {
        while (++index < length) {
          result[index] = callback(collection[index], index, collection);
        }
      } else {
        baseEach(collection, function(value, key, collection) {
          result[++index] = callback(value, key, collection);
        });
      }
      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 provided for `callback` the created "_.pluck" style
callback will return the property value of the given element.

If an object is provided for `callback` the created "_.where" style callback
will return `true` for elements that have the properties 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 provided it will be used
 to create a "_.pluck" or "_.where" style callback, respectively.
@param {*} [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] (property order is not guaranteed across environments)

var characters = [
  { 'name': 'barney', 'age': 36 },
  { 'name': 'fred',   'age': 40 }
];

// using "_.pluck" callback shorthand
_.map(characters, 'name');
// => ['barney', 'fred']