JS 中面向对象的5种写法

//第1种写法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()); 

//第2种写法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 ) );

//第3种写法var Circle = new Object();Circle.PI = 3.14159;Circle.Area = function( r ) {       return this.PI * r * r;}alert( Circle.Area( 1.0 ) );

//第4种写法var Circle={   "PI":3.14159, "area":function(r){          return this.PI * r * r;        }};alert( Circle.area(1.0) );

//第5种写法var Circle = new Function("this.PI = 3.14159;this.area = function( r ) {return r*r*this.PI;}");alert( (new Circle()).area(1.0) );