首先 定义circle类,拥有成员变量r,常量PI和计算面积的成员函数area();
//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
) );