JSFiddle - React, Tailwind, and code Playground

HTML

<div class="add-to-favourites">Two Words</div>
<div class="add-to-favourites">OneWords</div>
<div class="add-to-favourites">NoSpaces</div>
FAV:
<ul id="favourites"></ul>

JavaScript

$(function () {
$('.add-to-favourites').click(function() {
   var num = $(this).text();
   var numClass = num.replace(" ", "_" );
   var $fav = $('#favourites');
   var $fav_li = $fav.find('.' + numClass  + '_li');

   if ($fav_li.length) {
      $fav_li.remove();
   } else {
      $('#favourites').append('<li class="' + numClass  + '_li">' + num + '</li>');
   }
})
});