classical.js

// as an approximation of the classical model, Num will return an object with methods on it
// these methods cannot be added to at run-time for all numbers, since there's no prototype
// chain going on here

var Num = function(val){
  return {
    val: val,
    mul: function(val) { return Num(this.val * val) },
    div: function(val) { return Num(this.val / val) },
    add: function(val) { return Num(this.val + val) },
    sub: function(val) { return Num(this.val + val) }
  }
}

var one = Num(1)
var two = one.add(1)

prototypal.js

var extend = function(t, f){ for ( var p in f ) t[p] = f[p]; return t; }
var derive = function(parent, o){ return extend(Object.create(parent), o) };

// here, we have a number prototype, which can be extended at runtime.  all numbers 
// will inherit from this
var Num = { 
  mul: function(val) { return derive(Num, { val: this.val * val }) },
  div: function(val) { return derive(Num, { val: this.val / val }) },
  add: function(val) { return derive(Num, { val: this.val + val }) },
  sub: function(val) { return derive(Num, { val: this.val - val }) }
}

var one = derive(Num, { val: 1 })
var two = one.add(1)