Inheritance in JavaScript

gistfile1.js

var d1, d2, d3, d4
function Base() {this.foo = 'foo'}
Base.prototype.bar = 'bar'

// Superconstructor
function D1() {Base.call(this)}
// Set prototype to instance
function D2() { }
D2.prototype = new Base()
// Set prototype to Base.prototype
function D3() { }
D3.prototype = Base.prototype
// Set prototype to new Object(), whose prototype is Base.prototype
function D4() { }
D4.prototype = Object.create(Base.prototype)

d1 = new D1()
d2 = new D2()
d3 = new D3()
d4 = new D4()

console.log(d1.foo, d1.bar)
//-> foo undefined
console.log(d2.foo, d2.bar)
//-> foo bar
console.log(d3.foo, d3.bar)
//-> undefined bar
console.log(d4.foo, d4.bar)
//-> undefined bar