Make iterator more prone to JIT optimizationsiterator-jit

1 files changed, 29 insertions, 22 deletions

diff --git a/lib/internal/iterator.js b/lib/internal/iterator.js
index 645dcbd..15c6fdd 100644
--- a/lib/internal/iterator.js
+++ b/lib/internal/iterator.js
@@ -2,33 +2,40 @@ import isArrayLike from 'lodash/isArrayLike';
 import getIterator from './getIterator';
 import keys from 'lodash/keys';
 
-export default function iterator(coll) {
+function createArrayIterator(coll) {
     var i = -1;
-    var len;
-    if (isArrayLike(coll)) {
-        len = coll.length;
-        return function next() {
-            i++;
-            return i < len ? {value: coll[i], key: i} : null;
-        };
+    var len = coll.length;
+    return function next() {
+        return ++i < len ? {value: coll[i], key: i} : null;
     }
+}
 
-    var iterate = getIterator(coll);
-    if (iterate) {
-        return function next() {
-            var item = iterate.next();
-            if (item.done)
-                return null;
-            i++;
-            return {value: item.value, key: i};
-        };
+function createES2015Iterator(iterator) {
+    var i = -1;
+    return function next() {
+        var item = iterator.next();
+        if (item.done)
+            return null;
+        i++;
+        return {value: item.value, key: i};
     }
+}
 
-    var okeys = keys(coll);
-    len = okeys.length;
+function createObjectIterator(obj) {
+    var okeys = keys(obj);
+    var i = -1;
+    var len = okeys.length;
     return function next() {
-        i++;
-        var key = okeys[i];
-        return i < len ? {value: coll[key], key: key} : null;
+        var key = okeys[++i];
+        return i < len ? {value: obj[key], key: key} : null;
     };
 }
+
+export default function iterator(coll) {
+    if (isArrayLike(coll)) {
+        return createArrayIterator(coll);
+    }
+
+    var iterator = getIterator(coll);
+    return iterator ? createES2015Iterator(iterator) : createObjectIterator(coll);
+}