collection/filter.js

define(['../internal/arrayFilter', '../internal/baseCallback', '../internal/baseFilter', '../lang/isArray'], function(arrayFilter, baseCallback, baseFilter, isArray) {

  /**
   * Iterates over elements of `collection`, returning an array of all elements
   * `predicate` returns truthy 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 _
   * @alias select
   * @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 new filtered array.
   * @example
   *
   * var evens = _.filter([1, 2, 3, 4], function(n) { return n % 2 == 0; });
   * // => [2, 4]
   *
   * var users = [
   *   { 'user': 'barney', 'age': 36, 'active': false },
   *   { 'user': 'fred',   'age': 40, 'active': true }
   * ];
   *
   * // using the "_.property" callback shorthand
   * _.pluck(_.filter(users, 'active'), 'user');
   * // => ['fred']
   *
   * // using the "_.matches" callback shorthand
   * _.pluck(_.filter(users, { 'age': 36 }), 'user');
   * // => ['barney']
   */
  function filter(collection, predicate, thisArg) {
    var func = isArray(collection) ? arrayFilter : baseFilter;
    predicate = baseCallback(predicate, thisArg, 3);
    return func(collection, predicate);
  }

  return filter;
});