Several methods of JS object-oriented 2

Define the Circle class, member function area () with member variable r, constant pi, and calculated areas

1. Factory mode

var Circle = function () {   var obj = new Object ();   Obj. PI = 3.14159;      Obj.area = function (r) {       return this. PI * R * r;   }   return obj;} var c = new Circle (); Alert (C.area (1.0));

2. More formal wording

function Circle (r) {      THIS.R = r;} Circle.pi = 3.14159; Circle.prototype.area = function () {  return circle.pi * THIS.R * THIS.R;} var c = new Circle (1.0);   

3.json notation

var circle={   ' PI ': 3.14159, ' area ': function (r) {          return this. PI * R * r;        }; Alert (Circle.area (1.0));

4. A little change, but essentially the same as the first

var circle=function (r) {        this.r=r;} Circle.pi = 3.14159; circle.prototype={    area:function () {        return this.r*this.r*circle.pi;    }} var obj=new Circle (1.0); alert (Obj.area ())

Circle.pi = 3.14159; Can be put into the attribute to write this. pi=3.14159;

Commonly used for the first and third types of

An extended small instance of the third type of notation

var show={        btn:$ ('. Div1 '),        init:function () {            var that=this;            alert (this);            This.btn.click (function () {                    that.change ();                    Alert (this)                ,})                    },        change:function () {            this.btn.css ({' Background ': ' Green '});        }    }    Show.init ();

JS Object-oriented methods 2