Question

Is it possible to know the elements old value and new value when it is changed dynamically?

An example, I have a button with value 190

<button name="btn1" directiveX>190</button>

And this button will be changed dynamically by socket.io. When its changed, I need to compare these values, if the new value higher then the old value is.

Thank You!

Answer 1

If you $watch the value in your scope, it will give you the old value and the new value. So your link function in the directive would look like this

link: function(scope, element, attrs) {
         scope.$watch("foo", function(newVal, oldVal) {
           //logic based on oldVal
         }
      }

And then in your HTML

<button name="btn1" directiveX>{{foo}}</button>

See http://docs.angularjs.org/api/ng.$rootScope.Scope