JS 中面向对象的5钟写法

JS 中面向对象的5钟写法
  //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()); 

1. //第2种写法 
2. var Circle = function() { 
3.    var obj = new Object(); 
4.    obj.PI = 3.14159; 
5.     
6.    obj.area = function( r ) { 
7.        return this.PI * r * r; 
8.    } 
9.    return obj; 
10. } 
11.  
12. var c = new Circle(); 
13. 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 ) );

1. //第4种写法 
2. var Circle={ 
3.    "PI":3.14159, 
4. "area":function(r){ 
5.           return this.PI * r * r; 
6.         } 
7. }; 
8. alert( Circle.area(1.0) ); 

1. //第5种写法 
2. var Circle = new Function("this.PI = 3.14159;this.area = function( r ) {return r*r*this.PI;}"); 
3.  
4. alert( (new Circle()).area(1.0) );