JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.20.1/moment.min.js"></script>
<div class="countdown" data-end="1519302600"></div>
<div class="countdown" data-end="1519776000"></div>

JavaScript

function countdown(el, interval) {
  const end = moment.unix(el.dataset.end);
  const dur = moment.duration(end.diff(moment()));
  
  let html = ''
  if(dur.hours() > 0) {
  	const hours = Math.floor(dur.asHours(true));
  	html += hours + ' ' + plural(hours, 'hour') + ', ';
  }
  if(dur.minutes() > 0) {
  	html += dur.minutes() + ' ' + plural(dur.minutes(), 'minute') + ', ';
  }
  if(dur.seconds() > 0) {
  	html += dur.seconds() + ' ' + plural(dur.seconds(), 'second') + ', ';
  }
  html = html.slice(0, -2);
  
  // already happend
  if(dur <= 0) {
  	clearInterval(interval);
  	html = 'Now';
  }
  el.innerHTML = html;
}

function plural(n, word) {
	return word + ((n === 1) ? '' : 's');
}

const elements = document.getElementsByClassName('countdown');
Array.prototype.forEach.call(elements, function (el) {
	const interval = setInterval(function() {
    countdown(el, interval);
  }, 1000);
});