JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box">
 test
</div>

CSS

#box {
 position:absolute;
 width:auto;
 background:#99ccff;
 border:1px solid #003366;
}

JavaScript

function animate() {
        xnow = parseInt(item.style.left);
        item.style.left = (xnow+1)+'px';
        ynow = parseInt(item.style.top);
        item.style.top = (ynow+Math.sin(2*Math.PI*(xnow/50))*10) + "px";
        setTimeout(animate,20);
    }

item = document.getElementById('box'); 
item.style.left = '0px'; 
item.style.top = '400px';
animate();