Just the Basics, for people who hate JavaScript libraries (like me!)

common.js

/*
    I've never been a fan of JavaScript frameworks.
    These three functions are all I ever really need!
*/

/* convenient DOM element lookup */
function $(el){
    return document.getElementById(el);
}

/* easy closure generation */
Function.prototype.bind = function(scope){
    var __self = this;
    return function(){
        return __self.apply(scope, arguments);
    };
};

/* simple inheritance, the JavaScript way */
Function.prototype.extends = function(superclass){
    this.superclass = superclass;
    this.prototype = Object.create(superclass.prototype, {
        constructor: {
            value: this,
            enumerable: false,
            writable: true,
            configurable: true
        }
    });
};

The first two functions are rough bastardizations of Prototype functions from the good ol' days. The third function is a slight adaption of Node's util.inherits method.