How to get difference between 2 dates in HH:MM:SS format in javascript ?

function getDateObject(datestr) {
          var parts = datestr.split(' ');
          var dateparts = parts[0].split('-');
          var day = dateparts[0];
          var month = parseInt(dateparts[1]) - 1;
          var year = dateparts[2];
          var timeparts = parts[1].split(':')
          var hh = timeparts[0];
          var mm = timeparts[1];
          var ss = timeparts[2];
          var date = new Date(year, month, day, hh, mm, ss, 00);
          return date;
      }

      function gettimediff(t1, t2) {
          var t1val = Number( t1.getHours() * 60 + t1.getMinutes());
          var t2val = Number(t2.getHours() * 60 + t2.getMinutes());
          var min = Math.floor((t2val - t1val) % 60);
          var hours = parseInt((t2 - t1) / (1000 * 60 * 60));
          return (hours + ':' + min + ':00');
      }

      var from = '03-04-2017 08:00:00';
      var to = '04-04-2017 09:00:00';
      from = getDateObject(from);
      to = getDateObject(to);

      alert(gettimediff(from, to)); //25:0:00