Bump to v4.0.0.

findKey.js

@@ -0,0 +1,41 @@
+define(['./internal/baseFind', './internal/baseForOwn', './internal/baseIteratee'], function(baseFind, baseForOwn, baseIteratee) {
+
+  /**
+   * This method is like `_.find` except that it returns the key of the first
+   * element `predicate` returns truthy for instead of the element itself.
+   *
+   * @static
+   * @memberOf _
+   * @category Object
+   * @param {Object} object The object to search.
+   * @param {Function|Object|string} [predicate=_.identity] The function invoked per iteration.
+   * @returns {string|undefined} Returns the key of the matched element, else `undefined`.
+   * @example
+   *
+   * var users = {
+   *   'barney':  { 'age': 36, 'active': true },
+   *   'fred':    { 'age': 40, 'active': false },
+   *   'pebbles': { 'age': 1,  'active': true }
+   * };
+   *
+   * _.findKey(users, function(o) { return o.age < 40; });
+   * // => 'barney' (iteration order is not guaranteed)
+   *
+   * // using the `_.matches` iteratee shorthand
+   * _.findKey(users, { 'age': 1, 'active': true });
+   * // => 'pebbles'
+   *
+   * // using the `_.matchesProperty` iteratee shorthand
+   * _.findKey(users, ['active', false]);
+   * // => 'fred'
+   *
+   * // using the `_.property` iteratee shorthand
+   * _.findKey(users, 'active');
+   * // => 'barney'
+   */
+  function findKey(object, predicate) {
+    return baseFind(object, baseIteratee(predicate, 3), baseForOwn, true);
+  }
+
+  return findKey;
+});