JSFiddle - React, Tailwind, and code Playground

HTML

<div id="block"></div>

CSS

#block{
    width: 50px; height: 50px; background:#f00;
    position: absolute; top: 100px; left: 0;
}

JavaScript

var blk = $('#block'); 
function anim(){
    var lft= parseInt(blk.css('left')) > 0? 0 : 200;
    blk.animate({left: lft}, 'fast', function(){
        window.setTimeout(anim, 700)
    })
}
anim();