JSFiddle - React, Tailwind, and code Playground

HTML

<div id="clockdiv"></div>

JavaScript

var deadline = 'June 20 2016';

function getTimeRemaining(endtime){
  var t = Date.parse(endtime) - Date.parse(new Date());
  var seconds = Math.floor( (t/1000) % 60 );
  var minutes = Math.floor( (t/1000/60) % 60 );
  var hours = Math.floor( (t/(1000*60*60)) % 24 );
  var days = Math.floor( t/(1000*60*60*24) );
  return {
    'total': t,
    'days': days,
    'hours': hours,
    'minutes': minutes,
    'seconds': seconds
  };
}

function initializeClock(id, endtime){
  var clock = document.getElementById(id);
  var timeinterval = setInterval(function(){
    var t = getTimeRemaining(endtime);
    clock.innerHTML = 'days: ' + t.days + '<br>' +
                      'hours: '+ t.hours + '<br>' +
                      'minutes: ' + t.minutes + '<br>' +
                      'seconds: ' + t.seconds;
    if(t.total<=0){
      clearInterval(timeinterval);
    }
  },1000);
}


initializeClock('clockdiv', deadline);