JSFiddle - React, Tailwind, and code Playground

HTML

<div class="overlay"></div>
<div class="popup">Some popup text</div>
<p>Some content text (click anywhere to toggle overlay)</p>

CSS

html,
body {
    height: 100%;
}
.overlay {
 	position:absolute;
	display:none; 

    /* color with alpha transparency */
    background-color: rgba(0, 0, 0, 0.7);

    /* stretch to screen edges */
    top: 0;
	left: 0;
    bottom: 0;
    right: 0;
}
.popup {
    position: absolute;
    width: 300px;
    height: 150px;
    display: none;
    background-color: white;
    text-align: center;

    /* center it ? */
    top: 50%;
    left: 50%;
    margin-left: -150px;
    margin-top: -75px;
}

JavaScript

$("body").click(function(){
    $(".overlay, .popup").fadeToggle();
})