JSFiddle - React, Tailwind, and code Playground

HTML

<div id="foo" style="width: 50px; height: 50px; background: orange;"></div>

JavaScript

/* Example 1: Alt-Click on div#foo */
Element.Events.altClick = {
    base: "click",
    condition: function(e) {
        return e.alt;
    }
};
var clicks = 0;
$("foo").addEvent("altClick", function(e) {
    clicks++;
    this.set("text", clicks);
});

/* Example 2: Shift-H Shortcut */
Element.Events.shiftH = {
    base: "keypress",
    condition: function(e) {
        if (e.shift && e.key == "h") { return true; }
    }
};
window.addEvent("shiftH", function() {
    var div = $("foo");
    var opacity = (div.get("opacity") == 0 ? 1 : 0);
    div.tween("opacity", opacity);
});