Attach multiple events (click, load, etc) to a DOM element

attachDomEvent.js

(function(){
    'use strict';

    Object.prototype.attachDomEvent = function(eventName, callback)
    {
        eventName = eventName.replace(/^on/g, '');

        if ( window.addEventListener ) {
            this.addEventListener(eventName, callback, false);            
        } else if ( window.attachEvent ) {
            this.attachEvent('on'+eventName, callback);            
        } else {
            var registered = this['on' + eventName];
            this['on' + eventName] = registered ? function(e) {
                registered(e);
                callback(e);
            } : callback;
        }
        
        return this;
    }
})();

// examples

window.attachDomEvent('onload', function(){
    alert('Loaded!')
});

document.getElementById('button').attachDomEvent('onclick', function(){
    alert('Clicked!')
}).attachDomEvent('onclick', function(){
    alert('Did I say clicked?')
});