Fixes jashkenas#770 -- reverts each array-like semantics change.

test/collections.js

@@ -44,6 +44,17 @@ $(document).ready(function() {
     var doubled = _([1, 2, 3]).map(function(num){ return num * 2; });
     equal(doubled.join(', '), '2, 4, 6', 'OO-style doubled numbers');
 
+    if (document.querySelectorAll) {
+      var ids = _.map(document.querySelectorAll('#map-test *'), function(n){ return n.id; });
+      deepEqual(ids, ['id1', 'id2'], 'Can use collection methods on NodeLists.');
+    }
+
+    var ids = _.map($('#map-test').children(), function(n){ return n.id; });
+    deepEqual(ids, ['id1', 'id2'], 'Can use collection methods on jQuery Array-likes.');
+
+    var ids = _.map(document.images, function(n){ return n.id; });
+    ok(ids[0] == 'chart_image', 'can use collection methods on HTMLCollections');
+
     var ifnull = _.map(null, function(){});
     ok(_.isArray(ifnull) && ifnull.length === 0, 'handles a null properly');
   });

underscore.js

@@ -80,7 +80,7 @@
     if (obj == null) return;
     if (nativeForEach && obj.forEach === nativeForEach) {
       obj.forEach(iterator, context);
-    } else if (_.isArray(obj) || _.isArguments(obj)) {
+    } else if (obj.length === +obj.length) {
       for (var i = 0, l = obj.length; i < l; i++) {
         if (iterator.call(context, obj[i], i, obj) === breaker) return;
       }