Javascript OOP

javascript_oop.js

var Parent = function(name) { // constructor
  this.name = name; // own property
};

// Function.prototype
(function(proto) {
  // shared method
  proto.toString = function() { return '** Parent ' + this.name; };
})(Parent.prototype);

var Child = function(name) {
  Parent.call(this, name); // constructor stealing
};
Child.prototype = Object.create(Parent.prototype); // prototype chaining

(function(proto) {
  // Function.prototype.constructor
  proto.constructor = Child;
  // method redefinition
  proto.toString = function() { return '** Child ' + this.name; };
})(Child.prototype);

var p = new Parent('PARENT');
var ch = new Child('CHILD');

console.log(p.toString()); // ** Parent PARENT
console.log(ch.toString()); // ** Child CHILD
// call parent method
console.log(Parent.prototype.toString.call(ch)); // ** Parent CHILD
console.log(p instanceof Parent); // true
console.log(p instanceof Child); // false
console.log(ch instanceof Parent); // true
console.log(ch instanceof Child); // true
console.log(p.constructor === Parent); // true
console.log(ch.constructor === Child); // true