--- /dev/null
+'use strict';
+module.exports = function (arr, predicate, ctx) {
+ if (typeof Array.prototype.findIndex === 'function') {
+ return arr.findIndex(predicate, ctx);
+ }
+
+ if (typeof predicate !== 'function') {
+ throw new TypeError('predicate must be a function');
+ }
+
+ var list = Object(arr);
+ var len = list.length;
+
+ if (len === 0) {
+ return -1;
+ }
+
+ for (var i = 0; i < len; i++) {
+ if (predicate.call(ctx, list[i], i, list)) {
+ return i;
+ }
+ }
+
+ return -1;
+};