JSFiddle - React, Tailwind, and code Playground

by Bikram Shrestha

HTML

<div id="box">hello</div>

CSS

#box{
    height:300px;
    width:300px;
    background:#ccc
}

JavaScript

var popit = true;
     window.onbeforeunload = function() { 
          if(popit == true) {
               popit = false;
               return "Are you sure you want to leave?"; 
          }
     }