JSFiddle - React, Tailwind, and code Playground

HTML

<p id="div">

</p>

CSS

.p{
  font-size:146;
}

JavaScript

var div = document.createElement('div');
        div.setAttribute('data-size','my_data');
        div.innerHTML = "I am a d222iv";
        div.id='someone';
        document.body.appendChild(div);

 var mydata = document.getElementById('someone').getAttribute('data-size');
alert(mydata);