JSFiddle - React, Tailwind, and code Playground

HTML

<div id="hero">
</div>

CSS

#hero{
    background-color: #f00;
    width: 20px;
    height: 20px;
}

JavaScript

var kleur="#f00";
setInterval(gameloop,1000);

function gameloop()
{
	if(kleur== "#f00")
    {
        kleur="#ff0";
    }else
    {
        kleur="#f00";
    }
    var hero_variable=document.getElementById("hero");
	hero_variable.style.backgroundColor=kleur; 
}