JSFiddle - React, Tailwind, and code Playground

by shomz

HTML

<div id="x"></div>

JavaScript

var x = false;
document.getElementById('x').innerHTML = x;
window.onbeforeunload = function(e) {
    x = true;
    document.getElementById('x').innerHTML = x;
 return "Click STAY ON PAGE then SAVE to save any data you've entered.\n If you've already SAVED select LEAVE PAGE to continue."; 
}