Javascript物件導向的5鐘寫法

定義Circle類，擁有成員變數r，常量PI和計算面積的成員函數area()

Javascript代碼

//第1種寫法 
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()); 

Javascript代碼

//第2種寫法 
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 ) ); 

Javascript代碼

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

Javascript代碼

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

Javascript代碼

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