angular Watch

HTML

<script src="https://code.angularjs.org/1.2.9/angular.min.js"></script>
<div ng-controller="MyCtrl"></div>

JavaScript

var myApp = angular.module('myApp',[]);
function MyCtrl ($scope) {

var testValue = null;
    $scope.watchMe = null;
        
    $scope.$watch('watchMe', function () {
    console.log('testValue is', testValue);
        
        if(testValue !== null){
            console.log('i want to do something different the 2nd time this code runs - but i never get in here...');
        }
    testValue ="changed";
    });
   
};