JSFiddle - React, Tailwind, and code Playground

HTML

<div id="testDiv" style="width:20px;height:20px;background:red;float:left;margin:10"></div>

JavaScript

var testDiv = document.getElementById('testDiv'),
    i         = 0;
// loop function
var loop = function () {
    // if margin left become 100px I set it again on 0px
    if (i == 500) {
        i = 0;
    }
    // increasing testing div's margin left 
    testDiv.style.marginLeft = i+'px';
    i++;

}
// first init
loop ();
// loop is executed every 30 ms
var interval = setInterval(loop,50);