JSFiddle - React, Tailwind, and code Playground

CSS

.testDiv { 
    width:100%; 
    height:100px; 
    border: 1px solid black;
}

JavaScript

$(document).ready(function(){
 var div = "<div class='testDiv'>Div Content</div>";
   $("body").append(div);
 alert($("div.testDiv").width());

});