Javascript prototypical inheritance by example

// Util.inherits - straight from node js sourcecode
var util = {
  inherits: function (ctor, superCtor) {
    ctor.super_ = superCtor;
    ctor.prototype = Object.create(superCtor.prototype, {
      constructor: {
        value: ctor,
        enumerable: false,
        writable: true,
        configurable: true
      }
    });
  }
};

var Other = function () {

};

Other.prototype.stuff = function () {
  console.log('Other!');
}

// create our Base constructor
var Base = function (a) {
  this.a = a;
  this.other = new Other();
};

// add a prototype method
Base.prototype.add = function () {
  this.a++;
};

Base.prototype.callStuff = function () {
  this.other.stuff();
}

/* ... */

// An ancestor of Base constructor
var ChildBase = function (b) {
  // we have to invoke the Base consturctor with the current context.
  Base.apply(this, arguments);

  this.b = b;
};
// here is where inheritance happens
util.inherits(ChildBase, Base);

/* ... */

ChildBase.prototype.callOther = function () {
  this.callStuff();
};

// instantiation
var childBase = new ChildBase(2);
// JS keyword instanceof works
console.log(childBase instanceof ChildBase); // true
console.log(childBase instanceof Base); // true
childBase.add();
console.log(childBase.a); // value will be 3
console.log(childBase.b); // value will be 2
childBase.callOther() // 'Other!'