--- /dev/null
+var baseFindIndex = require('./_baseFindIndex'),
+ baseIteratee = require('./_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
+ *
+ * // The `_.matches` iteratee shorthand.
+ * _.findIndex(users, { 'user': 'fred', 'active': false });
+ * // => 1
+ *
+ * // The `_.matchesProperty` iteratee shorthand.
+ * _.findIndex(users, ['active', false]);
+ * // => 0
+ *
+ * // The `_.property` iteratee shorthand.
+ * _.findIndex(users, 'active');
+ * // => 2
+ */
+function findIndex(array, predicate) {
+ return (array && array.length)
+ ? baseFindIndex(array, baseIteratee(predicate, 3))
+ : -1;
+}
+
+module.exports = findIndex;