JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
   <span>FirstName</span>
   <br />
   <input type="text" />
</div>

CSS

#container {
    width: 300px;    
    background: #acf;
    border: 3px solid #999;
    position : absolute;
}

JavaScript

console.log($('#container input').height());
alert($('#container input').height());