Bump to v4.0.0.

findIndex.js

@@ -0,0 +1,43 @@
+import baseFindIndex from './internal/baseFindIndex';
+import baseIteratee from './internal/baseIteratee';
+
+/**
+ * This method is like `_.find` except that it returns the index of the first
+ * element `predicate` returns truthy for instead of the element itself.
+ *
+ * @static
+ * @memberOf _
+ * @category Array
+ * @param {Array} array The array to search.
+ * @param {Function|Object|string} [predicate=_.identity] The function invoked per iteration.
+ * @returns {number} Returns the index of the found element, else `-1`.
+ * @example
+ *
+ * var users = [
+ *   { 'user': 'barney',  'active': false },
+ *   { 'user': 'fred',    'active': false },
+ *   { 'user': 'pebbles', 'active': true }
+ * ];
+ *
+ * _.findIndex(users, function(o) { return o.user == 'barney'; });
+ * // => 0
+ *
+ * // using the `_.matches` iteratee shorthand
+ * _.findIndex(users, { 'user': 'fred', 'active': false });
+ * // => 1
+ *
+ * // using the `_.matchesProperty` iteratee shorthand
+ * _.findIndex(users, ['active', false]);
+ * // => 0
+ *
+ * // using the `_.property` iteratee shorthand
+ * _.findIndex(users, 'active');
+ * // => 2
+ */
+function findIndex(array, predicate) {
+  return (array && array.length)
+    ? baseFindIndex(array, baseIteratee(predicate, 3))
+    : -1;
+}
+
+export default findIndex;