归纳下js面向对象的几种常见写法总结

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 ) );

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);  alert(c.area());

var Circle={  "PI":3.14159, "area":function(r){     return this.PI * r * r;    }};alert( Circle.area(1.0) );

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())

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();