JSFiddle - React, Tailwind, and code Playground

HTML

<div>test.</div>

JavaScript

window.onload = function ()
{
    document.onmousedown = function(e) {
        e = e || window.event;
        alert("window.event " + (window.event ? "existe" : "n'existe pas") + "\nBouton pressé : " + e.button);
    }
}