JSFiddle - React, Tailwind, and code Playground
HTML
<div id="message"></div>
<div id="content">
</div>
<nav>
<ul>
<li><a href="http://google.fr">Google</a></li>
<li><a href="http://yahoo.fr">Yahoo</a></li>
<li><a href="http://tf1.fr">Tf1</a></li>
</ul>
</nav>
JavaScript
$(document).on('click','nav ul li a',function(e){
e.preventDefault();
var cloneLink = $(this).clone();
var attrActive = $(this).attr('href');
var length;
length = $('#content').children('a[href="'+attrActive+'"]').length;
if(length == 1){
$('#message').html("pas bon");
}
else {
$('#content').last().append(cloneLink);
}
});