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: 70px;
    left: 0;
    display: none;
    z-index: 9998;
}
.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").slideToggle("fast");
});