title: Observing ES6 Module properties
body: <p>I have a module:</p>
  
  <pre><code>var progress = {
      val: 0
  };
  
  var service = (function(){
  
      function someMethod(){
          progress.val++;
      }
  
      return{
          someMethod: someMethod
      };
  
  })();
  
  export {service,progress}
  </code></pre>
  
  <p><code>someMethod</code> will perform an operation where an array is iterated. I would like to increment <code>progress.val</code> by one at each iteration. This progress should then be observable:</p>
  
  <pre><code>  System.import('components/Service.js')
     .then(function(M){
              self.progress = M.progress;
  
             Object.observe(M.progress,function(c){
                 console.dir(c);
             });
         });
  </code></pre>
  
  <p>Unfortunately, the observers callback is invoked only once, holding an array of changes with one item per iteration.</p>
  
  <p>How can I invoke the callback on each iteration? </p>