fix(jqLite): ignore class methods on comment elements

Since c785267 jqLite uses setAttribute (rather than className property) in order to change classes. Some elements (eg. Comment) do not have this method which blows up.

jQuery silently ignores these method calls (because it uses className), so to get the same behavior as jQuery, we check for setAttribute method first.

src/jqLite.js

@@ -279,12 +279,13 @@ function JQLiteData(element, key, value) {
 }
 
 function JQLiteHasClass(element, selector) {
+  if (!element.getAttribute) return false;
   return ((" " + (element.getAttribute('class') || '') + " ").replace(/[\n\t]/g, " ").
       indexOf( " " + selector + " " ) > -1);
 }
 
 function JQLiteRemoveClass(element, cssClasses) {
-  if (cssClasses) {
+  if (cssClasses && element.setAttribute) {
     forEach(cssClasses.split(' '), function(cssClass) {
       element.setAttribute('class', trim(
           (" " + (element.getAttribute('class') || '') + " ")
@@ -296,7 +297,7 @@ function JQLiteRemoveClass(element, cssClasses) {
 }
 
 function JQLiteAddClass(element, cssClasses) {
-  if (cssClasses) {
+  if (cssClasses && element.setAttribute) {
     var existingClasses = (' ' + (element.getAttribute('class') || '') + ' ')
                             .replace(/[\n\t]/g, " ");
 

test/jqLiteSpec.js

@@ -493,6 +493,16 @@ describe('jqLite', function() {
     });
 
 
+    it('should ignore comment elements', function() {
+      var comment = jqLite(document.createComment('something'));
+
+      comment.addClass('whatever');
+      comment.hasClass('whatever');
+      comment.toggleClass('whatever');
+      comment.removeClass('whatever');
+    });
+
+
     describe('hasClass', function() {
       it('should check class', function() {
         var selector = jqLite([a, b]);