diff --git a/index.js b/index.js
index 0cb4ea4..d81be4b 100644
--- a/index.js
+++ b/index.js
@@ -13,8 +13,7 @@ module.exports = function (arr) {
 
 function flat(arr, res) {
   var i = 0, cur;
-  var len = arr.length;
-  for (; i < len; i++) {
+  for (; i < arr.length; i++) {
     cur = arr[i];
     Array.isArray(cur) ? flat(cur, res) : res.push(cur);
   }