lodash/collection/partition.js

define(['../internal/createAggregator'], function(createAggregator) {

  /**
   * Creates an array of elements split into two groups, the first of which
   * contains elements `predicate` returns truthy for, while the second of which
   * contains elements `predicate` returns falsey for. The predicate 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 {Function|Object|string} [predicate=_.identity] The function invoked
   *  per iteration. If a property name or object is provided it is used to
   *  create a "_.property" or "_.matches" style callback respectively.
   * @param {*} [thisArg] The `this` binding of `predicate`.
   * @returns {Array} Returns the array of grouped elements.
   * @example
   *
   * _.partition([1, 2, 3], function(n) { return n % 2; });
   * // => [[1, 3], [2]]
   *
   * _.partition([1.2, 2.3, 3.4], function(n) { return this.floor(n) % 2; }, Math);
   * // => [[1, 3], [2]]
   *
   * var users = [
   *   { 'user': 'barney',  'age': 36, 'active': false },
   *   { 'user': 'fred',    'age': 40, 'active': true },
   *   { 'user': 'pebbles', 'age': 1,  'active': false }
   * ];
   *
   * // using the "_.matches" callback shorthand
   * _.map(_.partition(users, { 'age': 1 }), function(array) { return _.pluck(array, 'user'); });
   * // => [['pebbles'], ['barney', 'fred']]
   *
   * // using the "_.property" callback shorthand
   * _.map(_.partition(users, 'active'), function(array) { return _.pluck(array, 'user'); });
   * // => [['fred'], ['barney', 'pebbles']]
   */
  var partition = createAggregator(function(result, value, key) {
    result[key ? 0 : 1].push(value);
  }, function() { return [[], []]; });

  return partition;
});