title: Why would you compare an old value and a new value with angular watch to see if they are equal
body: <p>I came across <a href="https://stackoverflow.com/a/25294989/3708225">this answer</a> in which the author is doing</p>
  
  <pre><code>$scope.$watch('myObject', function(newValue, oldValue){
      if(angular.equals(newValue, oldValue)){
           return; 
       }
  });
  </code></pre>
  
  <p>Why would newValue and oldValue ever be the same here?  My understanding of <code>$watch</code> is that it only fires when <code>myObject</code> changes.  What am I missing?</p>