A Brief History of JavaScript

Objects

literals
› o = {prop: val, ...}

properties
› get: x = o.p
› set, add: o.p = e
› delete: delete o.p

prototypes
› lookup along chain

> point = {x: 1, y: 2}
Object
 1. x: 1
 2. y: 2
 3. __proto__: Object
> point.x
1
> point.z
undefined
> point.z = 3
3
> point.z
3
> delete point.z
true
> point.z
undefined

> var Point = function (x, y) {this.x = x; this.y = y;}
undefined
> Point.prototype.magnitude = function () {return
Math.sqrt(this.x * this.x + this.y * this.y);}
function () {return Math.sqrt(this.x * this.x + this.y *
this.y);}
> p = new Point(1,2)
Point
> p.x
1
> p.magnitude
function () {return Math.sqrt(this.x * this.x + this.y *
this.y);}
> p.magnitude()
2.23606797749979