JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outside"></div>
<div id="insideAbsolute"></div>
<div id="insideRelative"></div>

<div class="testAbsolute">test position absolute</div>
<div class="testRelative">test position relative</div>

CSS

body{
    position : relative;
}

#insideAbsolute{
 	background-color:#f8f8f8;
	position: absolute;
	top:0;
	left:20%;
	width:60%;
	margin-top:35px;
	margin-bottom:35px;
	z-index:3;
	border-radius: 7px;
	box-shadow: 6px 6px 20px black;	
}
#insideAbsolute:after{
    content:'';
    height : 35px;
    width : 100%;
    position : absolute;
    bottom : -35px;
}

#insideRelative{
 	background-color:#f8f8f8;
	position: relative;
	top:0;
	left:20%;
	width:60%;
	margin-top:35px;
	margin-bottom:35px;
	z-index:3;
	border-radius: 7px;
	box-shadow: 6px 6px 20px black;	
}


#outside{
	position: fixed;
	left:0;
	top:0;
	height: 100%;
	width: 100%;
	background-color: black;
	opacity:0.7;
	z-index:2;
	background-attachment:fixed;
}

.test{
	z-index:1;
}

JavaScript

$('#outside').hide();
	$('#insideAbsolute').hide();
	$('#insideRelative').hide();
		
	$(document).on('click', '.testAbsolute', function () {
		$('#outside').show(0, function() { 
			$('#insideAbsolute').show(0, function() {
				$(this).html('<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>');
				$(document).on('click','#outside',function(){
					$('#insideAbsolute').html('');
					$('#outside').hide();	
				});		
			}); 
		});
 
	});  

	$(document).on('click', '.testRelative', function () {
		$('#outside').show(0, function() { 
			$('#insideRelative').show(0, function() {
				$(this).html('<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>');
				$(document).on('click','#outside',function(){
					$('#insideRelative').html('');
					$('#outside').hide();	
				});		
			}); 
		});
 
	});