A simple Javascript inheritance example

gistfile1.js

Function.prototype.extends = function (parent) {
  var ctor = function () {},
      proto = this.prototype;

  ctor.prototype = parent.prototype;
  this.prototype = new ctor;
  this.prototype.constructor = this;
  
  for (var key in proto) {
    this.prototype[key] = proto[key];
  }
};


function foo () {};
foo.prototype = {
  x: 5,
};

function bar () {};
bar.prototype = {
  y: 6,
  z: 7
};

// inherit!
bar.extends(foo);

var baz = new bar;
console.log(baz); // { x: 5, y: 6, z: 7 }
console.log(baz instanceof bar); // true
console.log(baz instanceof foo); // true