JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://code.jquery.com/ui/1.12.0/jquery-ui.min.js"></script>
<a href="https://stackoverflow.com">The best site for Dev</a>

JavaScript

(function ($) {
  'use strict';

$(window).bind('beforeunload', function(e) {
  e.preventDefault();
  $('<div title="Attention !">Vous souhaitez quitter cette page. Avez-vous enregistré les données du formulaire ? Si non, choisissez "rester sur la page" lors de l\'affichage de l\'alerte.</div>').dialog({
    modal:true,
    close: function(){$(this).dialog('destroy').remove();},
    position: { my: "center top", at: "center", of: window }
  });
  return "Random message to trigger the browser's native alert.";
});

}(jQuery));