JSFiddle - React, Tailwind, and code Playground

HTML

<a href="http://JSON.org">JSON</a>

JavaScript

var timeout;

function warning() {
    timeout = setTimeout(function() {
        alert('You stayed');
    }, 1000);
    return "You are leaving the page";
}

function noTimeout() {
    clearTimeout(timeout);
}

window.onbeforeunload = warning;
window.unload = noTimeout;