JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box"></div>
<div id="box2" style="display:none"></div>

CSS

div {
    width:50px;
    height:50px;
    border:1px solid gray;
}
div#box2 {
    background-color:red;
}

div{
    background-color:black;
}
div.on{
    background-color:white !important;
}

JavaScript

var interval = 300;
    
    flicker();
    
    function flicker()
    {
        $("#box").toggleClass('on');
        setTimeout(flicker, interval)
    }