JSFiddle - React, Tailwind, and code Playground

HTML

<header>
    <span class="notify-icon"></span> 
    <div class="notify-box">
        <div class="header">Notifications</div>
        <div class="content">
            <a href="one"></a>
            <a href="two"></a>
            <a href="three"></a>
            <a href="four"></a>
            <a href="five"></a>
            <a href="sixe"></a>
        </div>
    </div>
</header>

CSS

body {
    background: #CCC;
    margin: 0;
    padding: 0;
}

header {
    width: 100%;
    height: 60px;
    padding: 15px;
    background: blue;
    -webkit-box-sizing:	border-box;
	-moz-box-sizing: border-box;
	-o-box-sizing: border-box;
	-ms-box-sizing: border-box;
	box-sizing: border-box;
}

.notify-icon {
    display: block;
    width: 30px;
    height: 30px;
    background: #000;
    cursor: pointer;
    z-index: 9999;
    position: relative;
    -webkit-touch-callout: none;
	-webkit-user-select: none;
	-khtml-user-select: none;
	-moz-user-select: none;
	-ms-user-select: none;
	user-select: none;
}

.notify-box {
     width: 200px;
    background: #FFF;
    position: absolute;
    top: 50px;
    left: 0;
	opacity: 0;
    z-index: 9998;
    -webkit-transition:	all 0.15s;
	-moz-transition: all 0.15s;
	-o-transition: all 0.15s;
	-ms-transition: all 0.15s;
	transition: all 0.15s;
}

.notify-box.show {
    top: 70px;
    opacity: 1;
   
}

.notify-box:before {
	content: '';
	position: absolute;
	top: -20px;
    left: 20px;
	width: 0;
	height: 0;
	border-left: 10px solid transparent;
	border-right: 10px solid transparent;
	border-bottom: 20px solid #FFF;
}

.notify-box .header {
    width: 100%;
    height: 30px;
    line-height: 30px;
    border-bottom: 1px solid rgba(0,0,0,0.2);
    padding: 0 8px;
    -webkit-box-sizing:	border-box;
	-moz-box-sizing: border-box;
	-o-box-sizing: border-box;
	-ms-box-sizing: border-box;
	box-sizing: border-box;
}

.notify-box .content {
    width: 100%;
    height: 306px;
    overflow: auto;
}

.notify-box a {
    display: block;
    width: 100%;
    height: 50px;
    border-bottom: 1px solid rgba(0,0,0,0.2);
}

JavaScript

// Notify Box
	$(".notify-icon").click(function(){
		$(".notify-box").toggleClass('show');
		$(this).toggleClass('show');
		
	});