JSFiddle - React, Tailwind, and code Playground

HTML

<button id="timeIt">Start Timer</button>
<div id="time"></div>

JavaScript

function go() {

    var time = document.getElementById('time'),
      timeIt = document.getElementById('timeIt'),
      interval, count = 30;


      clearInterval(interval);
      interval = setInterval(hola, 500);


  function hola(){
    time.innerHTML = --count;
  }

}

go();