JavaScript Event Listener

attach-event.js

AttachEvent = function (element, type, handler) {
    if (element.addEventListener) {
        element.addEventListener(type, handler, false);
    }else if (element.attachEvent) {
        element.attachEvent('on' + type, handler);
    } else {
        element['on' + type] = handler;
    }
};

Use like so:

AttachEvent(document.body, 'myEvent', function () {
        document.body.className += ' event-fired';
});