turn array for ins into fors

lib/6to5/types/index.js

@@ -440,7 +440,7 @@ t.getIds = function (node, map, ignoreTypes) {
     if (t.isIdentifier(id)) {
       ids[id.name] = id;
     } else if (nodeKeys) {
-      for (i in nodeKeys) {
+      for (i = 0; i < nodeKeys.length; i++) {
         key = nodeKeys[i];
         if (id[key]) {
           search.push(id[key]);
@@ -448,7 +448,7 @@ t.getIds = function (node, map, ignoreTypes) {
         }
       }
     } else if (arrKeys) {
-      for (i in arrKeys) {
+      for (i = 0; i < arrKeys.length; i++) {
         key = arrKeys[i];
         search = search.concat(id[key] || []);
       }