Handle sparse arrays properly in Array#_each to match behavior with browsers' built-in Array#forEach (and ES5). [#790 state:resolved] (Andriy Tyurnikov, Yaffle, Andrew Dupont)

Author: savetheclocktower

CHANGELOG

@@ -1,3 +1,5 @@
+* Handle sparse arrays properly in `Array#_each` to match behavior with browsers' built-in `Array#forEach` (and ES5). [#790 state:resolved] (Andriy Tyurnikov, Yaffle, Andrew Dupont)
+
 * Make `Event.extend` work with legacy IE events in IE 9. (Andrew Dupont)
 
 * Stop appending `&_=` to the parameters for non-GET Ajax requests in Safari. We no longer support any version of Safari for which this is necessary. [#327 state:resolved] (John-David Dalton, Andrew Dupont)

src/lang/array.js

@@ -189,12 +189,13 @@ Array.from = $A;
       slice = arrayProto.slice,
       _each = arrayProto.forEach; // use native browser JS 1.6 implementation if available
 
-  function each(iterator) {
-    for (var i = 0, length = this.length; i < length; i++)
-      iterator(this[i]);
+  function each(iterator, context) {
+    for (var i = 0, length = this.length >>> 0; i < length; i++) {
+      if (i in this) iterator.call(context, this[i], i, this);
+    }
   }
   if (!_each) _each = each;
-
+  
   /**
    *  Array#clear() -> Array
    *

test/unit/array_test.js

@@ -42,7 +42,7 @@ new Test.Unit.Runner({
     this.assertEnumEqual([], $A(5));
     this.assertEnumEqual([], $A(true));
   },
-  
+
   testClear: function(){
     this.assertEnumEqual([], [].clear());
     this.assertEnumEqual([], [1].clear());
@@ -185,5 +185,11 @@ new Test.Unit.Runner({
   testConcat: function(){
     var args = (function() { return [].concat(arguments) })(1, 2);
     this.assertIdentical(1, args[0][0]);
+  },
+  
+  testEachOnSparseArrays: function() {
+    var sparseArray = [0, 1];
+    sparseArray[5] = 5;
+    this.assertEqual('[0, 1, 5]', sparseArray.inspect(), "Array#each should skip nonexistent keys in an array");
   }
 });