JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.17/themes/ui-lightness/jquery-ui.css">
<input type="button" value="Popup" onclick="window.popup();"/>
<input type="button" value="Exit" onclick="window.location.reload();"/>
<div id="dialog"></div>

CSS

input {
     font-size: 30px;  
    padding: 20px;
    margin: 10px;
}

JavaScript

window.popup = function(){
    $('#dialog').dialog('destroy');
    $('#dialog').dialog({
        modal: true,
        title: "popup"
    });
}
    
$(window).on('beforeunload', function() {
    return "Click false and try popup again.";
});