JSFiddle - React, Tailwind, and code Playground

HTML

<div id="countdown">

</div>

JavaScript

setInterval(function(){
	var start = new Date();
    var end   = new Date("2017-10-03");
    var diff  = Math.round((end.getTime() - start.getTime()) / 1000);
    var hours = Math.floor(diff / 3600);
    diff -= hours * 3600
    var minutes = Math.floor(diff / 60);
    diff -= minutes * 60;
    var seconds = diff % 60;
    if(document.getElementById('countdown')){
        document.getElementById('countdown').innerHTML = "<span>" 
        + hours + "</span> hours <span>" + minutes + "</span> minutes <span>" 
        + seconds + "</span> seconds";
    }
}, 1000);