fix(ngClass): ensure that ngClass only adds/removes the changed classes

ngClass works by removing all the former classes and then adding all the
new classes to the element during each watch change operation. This may
cause transition animations to never render. The ngClass directive will
now only add and remove the classes that change during each watch operation.

Closes #4960
Closes #4944

1 files changed, 2 insertions, 18 deletions

diff --git a/src/ng/compile.js b/src/ng/compile.js
index 4d83f379..ce3d0514 100644
--- a/src/ng/compile.js
+++ b/src/ng/compile.js
@@ -688,8 +688,8 @@ function $CompileProvider($provide) {
         if(key == 'class') {
           value = value || '';
           var current = this.$$element.attr('class') || '';
-          this.$removeClass(tokenDifference(current, value).join(' '));
-          this.$addClass(tokenDifference(value, current).join(' '));
+          this.$removeClass(tokenDifference(current, value));
+          this.$addClass(tokenDifference(value, current));
         } else {
           var booleanKey = getBooleanAttrName(this.$$element[0], key),
               normalizedVal,
@@ -747,22 +747,6 @@ function $CompileProvider($provide) {
             $exceptionHandler(e);
           }
         });
-
-        function tokenDifference(str1, str2) {
-          var values = [],
-              tokens1 = str1.split(/\s+/),
-              tokens2 = str2.split(/\s+/);
-
-          outer:
-          for(var i=0;i<tokens1.length;i++) {
-            var token = tokens1[i];
-            for(var j=0;j<tokens2.length;j++) {
-              if(token == tokens2[j]) continue outer;
-            }
-            values.push(token);
-          }
-          return values;
-        }
       },