title: How to get total hours HH:MM format using Moment.js?
body: <p>I want to calculate the week total time using Moment.js. Please advise.
  This is what I tried so far:</p>
  
  <pre><code>total = "00:00";
  for (var i in json_obj) {
  
      var timeEnd = json_obj[i].END;
      var timeStart = json_obj[i].START;
  
      var timeDiff = moment.utc(moment(timeEnd, "HH:mm:ss").diff(moment(timeStart, "HH:mm:ss"))).format("HH:mm");
      var res = timeDiff;
      total = moment().add(res);
  </code></pre>