JSFiddle - React, Tailwind, and code Playground

HTML

<div class="videodiv"></div>
<div id="hier" class="div2"></div>

CSS

.videodiv
{
    width:100%;
    height:100px;
    border:1px solid black;
}
.div2
{
    width:100px;
    height:300px;
    border:1px solid black;
    overflow:auto;
    word-break:break-all;
}

JavaScript

var width = $('.videodiv')[0]['clientWidth'];
document.getElementById("hier").innerHTML = width;