Update callback.js

src/js/validator/callback.js

@@ -17,7 +17,7 @@
         validate: function(validator, $field, options) {
             var value = $field.val();
             if (options.callback && 'function' == typeof options.callback) {
-                return options.callback.call(this, value, this);
+                return options.callback.call(this, value, validator);
             }
             return true;
         }