function sortBy(collection, iteratee, thisArg) {
	      var index = -1,
	          length = collection ? collection.length : 0,
	          result = isLength(length) ? Array(length) : [];

	      if (thisArg && isIterateeCall(collection, iteratee, thisArg)) {
	        iteratee = null;
	      }
	      iteratee = getCallback(iteratee, thisArg, 3);
	      baseEach(collection, function(value, key, collection) {
	        result[++index] = { 'criteria': iteratee(value, key, collection), 'index': index, 'value': value };
	      });
	      return baseSortBy(result, compareAscending);
	    }
Creates an array of elements, sorted in ascending order by the results of
running each element in a collection through `iteratee`. This method performs
a stable sort, that is, it preserves the original sort order of equal elements.
The `iteratee` is bound to `thisArg` and invoked with three arguments;
(value, index|key, collection).

If a property name is provided for `predicate` the created "_.property"
style callback returns the property value of the given element.

If an object is provided for `predicate` the created "_.matches" style
callback returns `true` for elements that have the properties of the given
object, else `false`.

@static
@memberOf _
@category Collection
@param {Array|Object|string} collection The collection to iterate over.
@param {Array|Function|Object|string} [iteratee=_.identity] The function
 invoked per iteration. If a property name or an object is provided it is
 used to create a "_.property" or "_.matches" style callback respectively.
@param {*} [thisArg] The `this` binding of `iteratee`.
@returns {Array} Returns the new sorted array.
@example

_.sortBy([1, 2, 3], function(n) { return Math.sin(n); });
// => [3, 1, 2]

_.sortBy([1, 2, 3], function(n) { return this.sin(n); }, Math);
// => [3, 1, 2]

var users = [
  { 'user': 'fred' },
  { 'user': 'pebbles' },
  { 'user': 'barney' }
];

// using the "_.property" callback shorthand
_.pluck(_.sortBy(users, 'user'), 'user');
// => ['barney', 'fred', 'pebbles']