JSFiddle - React, Tailwind, and code Playground

HTML

<a onclick="toggleDiv('myDiv');">Link</a>
<div id="myDiv">
    <span id="poo">stuff</span>
</div>

CSS

#myDiv {
    background:#aaa;
    display:none;
    padding:20px;
}

JavaScript

var openDiv;

function toggleDiv(divID) {
    $("#" + divID).fadeToggle(200, function() {
        openDiv = $(this).is(':visible') ? divID : null;
    });
}

$(document).click(function(e) {
    if (!$(e.target).closest('#'+openDiv).length) {
        toggleDiv(openDiv);
    }
});