JSFiddle - React, Tailwind, and code Playground

HTML

<img class="edit-img about-img" id="imageId" src="http://via.placeholder.com/350x150">

JavaScript

function getDimension () {
    var img = document.getElementById('imageId');

    var width = img.clientWidth;
    var height = img.clientHeight;
    alert(width);
}

window.onload = getDimension();