clone.js

// Clone this object and (optionally) append
// own properties of `other_object` to the newly cloned one.
// This is a convenience method over the Object#create
// Initial code from here: http://howtonode.org/prototypical-inheritance
// Amended with: http://msdn.microsoft.com/en-us/library/ff877835(VS.94).aspx,
// the part about the clone function.
Object.defineProperty(Object.prototype, 'clone', {
    get: function() {
        var self = this;

        return function(other) {
            var cloned = Object.create(self);

            if (!Object.isExtensible(self))
                return Object.preventExtensions(cloned);

            if (!other || typeof other != 'object')
                return cloned;

            Object
                .getOwnPropertyNames(other)
                .forEach(function(property) {
                    Object.defineProperty(cloned, property, Object.getOwnPropertyDescriptor(other, property));
                });

            return cloned;
        };
    }
});

proto-points.js

var puts;

if (typeof require == 'undefined') // rhino before modules
    puts = print;
else // node
    puts = require('sys').puts;



function uber(obj) { return Object.getPrototypeOf(obj); }

var p1 = Object.prototype.clone({
    x: 0,
    y: 1,
    add: function(other) {
        return this.clone({ x: this.x + other.x, y: this.y + other.y });
    },
    toString: function() {
        return this.x + '@' + this.y;
    },
});


puts(p1); // 0@1

var p2 = p1.clone({
    color: '#green',
    toString: function() {
        return this.color + ': ' + uber(this).toString();
    },
});

puts(p2);  // #green: 0@1

self-proto-points.js

var traits_point = Object.prototype.clone({
    toString: function() {
        return this.x + '@' + this.y;
    },
    add: function(other) {
        return this.clone({ x: this.x + other.x, y: this.y + other.y });
    },
});

var p0 = traits_point.clone({ x: 0, y: 0 });
var p1 = traits_point.clone({ x: -1, y: 2 });

puts(p0); // 0@0
puts(p0.add(p1)); // -1@2