JSFiddle - React, Tailwind, and code Playground

HTML

<div class="appHeader">
    <div>
        <a class="user" href="#">Welcome, <span>Name Lastname</span></a>
        <ul class="user-menu">
            <div></div>
            <li><a href="#">Menu item</a></li>
            <li><a href="#">Menu item</a></li>
            <li><a href="#">Menu item</a></li>
            <li><a href="#">Menu item</a></li>
        </ul>
    </div>
</div>

CSS

.appHeader ul.user-menu {
	display: none;
	position:absolute;
	z-index: 900;
	width: 150px;
	border: 1px solid #111111;
	background: #FFFFFF;
	box-shadow: 1px 1px 1px 0px rgba(0, 0, 0, 0.2);
	text-align: left;
	list-style: none;
	padding: 10px 0;
	-webkit-border-radius: 4px; 
 	-moz-border-radius: 4px; 
 	-ms-border-radius: 4px; 
 	-o-border-radius: 4px; 
 	border-radius: 4px; 
} 
.appHeader ul.user-menu li {
	margin:0;
	padding:0 10px;
	display: block;
}
.appHeader ul.user-menu li a {
	height: 15px;
	text-transform: none;
	background: #FFFFFF;
	line-height: 1em;
	font-size: 1em;
	display: block;
	text-decoration: none;
	color: #222222;
	padding:0;
	padding: 8px 10px;
	outline: none;
}
.appHeader ul.user-menu li a:hover { 
	background: #f2f2f2; 
	-webkit-border-radius: 3px;
	-moz-border-radius: 3px;
	-ms-border-radius: 3px;
	-o-border-radius: 3px;
	border-radius: 3px;
}
.appHeader ul.user-menu li a:active { 
	background: #CCCCCC; 
	color: #111111;
}
.appHeader ul.user-menu div {
	height: 8px;
	width: 16px;
	background: #FFF;
	margin:-18px 0 10px 120px;
	background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAICAYAAADwdn+XAAAABHNCSVQICAgIfAhkiAAAAAlwSFlzAAALEgAACxIB0t1+/AAAABx0RVh0U29mdHdhcmUAQWRvYmUgRmlyZXdvcmtzIENTNui8sowAAAAWdEVYdENyZWF0aW9uIFRpbWUAMTAvMTEvMTPXucnQAAAAq0lEQVQokZWOvQkCQRhE52oQY+EtiGhgIGaWYQlWcIVctFuDiV2ciSCYKQZrIBhfovFn4A/cuog+mGzeMIWZKYdzbiZpKekmaRFjXOd6RW7AOTeVtCrL8ixJVVV1JM1jjPuPspm1woNjCKG2J977GmiAYdpP5RHQeO/fcjKyBybZAaAP7HLyixBCDZwAWgNAD7h8k5MnB2BsZhIwALa/yMmTLdAVsPlHTp5c7xF5KrEWk1zGAAAAAElFTkSuQmCC) no-repeat;
}

JavaScript

$('.appHeader a.user').on('click', function() {
    $('.appHeader ul.user-menu').fadeIn('fast');
    $(document).mouseup(function (e) {
        var container = $('.appHeader ul.user-menu');
        if (!container.is(e.target) && container.has(e.target).length === 0) {
            $('.appHeader ul.user-menu').fadeOut('fast');
        }
    });
});