Object.prototype

var current = Object.prototype.valueOf;

// Since my property "-prop-value" is cross-cutting and isn't always
// on the same prototype chain, I want to modify Object.prototype: 
Object.prototype.valueOf = function() {
  if (this.hasOwnProperty('-prop-value')) {
    return this['-prop-value'];
  } else {
    // It doesn't look like one of my objects, so let's fall back on 
    // the default behavior by reproducing the current behavior as best we can.
    // The apply behaves like "super" in some other languages.
    // Even though valueOf() doesn't take arguments, some other hook may.
    return current.apply(this, arguments
  }
}

var Person = function(name) {
  this.name = name;
  this.canTalk = true;
};

Person.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name
  }
};

var Employee = function(name, title) {
  Person.call(this, name
  this.title = title;
};

Employee.prototype = Object.create(Person.prototype
Employee.prototype.constructor = Employee;

Employee.prototype.greet = function() {
  if (this.canTalk) {
    console.log('Hi, I am ' + this.name + ', the ' + this.title
  }
};

var Customer = function(name) {
  Person.call(this, name
};

Customer.prototype = Object.create(Person.prototype
Customer.prototype.constructor = Customer;

var Mime = function(name) {
  Person.call(this, name
  this.canTalk = false;
};

Mime.prototype = Object.create(Person.prototype
Mime.prototype.constructor = Mime;

var bob = new Employee('Bob', 'Builder'
var joe = new Customer('Joe'
var rg = new Employee('Red Green', 'Handyman'
var mike = new Customer('Mike'
var mime = new Mime('Mime'

bob.greet(
// Hi, I am Bob, the Builder

joe.greet(
// Hi, I am Joe

rg.greet(
// Hi, I am Red Green, the Handyman

mike.greet(
// Hi, I am Mike

mime.greet(