function sortBy(collection, iteratee, thisArg) {
	      if (collection == null) {
	        return [];
	      }
	      if (thisArg && isIterateeCall(collection, iteratee, thisArg)) {
	        iteratee = undefined;
	      }
	      var index = -1;
	      iteratee = getCallback(iteratee, thisArg, 3);

	      var result = baseMap(collection, function(value, key, collection) {
	        return { '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 `iteratee` the created `_.property`
style callback returns the property value of the given element.

If a value is also provided for `thisArg` the created `_.matchesProperty`
style callback returns `true` for elements that have a matching property
value, else `false`.

If an object is provided for `iteratee` 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 {Function|Object|string} [iteratee=_.identity] The function invoked
 per iteration.
@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']