JSFiddle - React, Tailwind, and code Playground

HTML

Body

CSS

html {
    background: blue;
}
body {
    background: red;
    margin: 0 auto;
    width: 80%;
    height: 3000px;
}

JavaScript

triggered = false;
$("body").on("mouseleave", function (e) {
    console.log(e.offsetY, $(window).scrollTop())
    if (e.offsetY - $(window).scrollTop() < 0 && !triggered) {
        triggered = true;
        alert("leave");
    }
});