JSFiddle - React, Tailwind, and code Playground

HTML

<div id="number">4</div>

JavaScript

setInterval(function(){
        var random = (Math.floor((Math.random()*15)+1)); 
        var currentnumber = parseInt(document.getElementById('number').innerHTML);
    console.log(currentnumber, random)

        document.getElementById('number').innerHTML =  currentnumber + random;

     }, 1000);