//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()
1.工厂方式
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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 ) );
2.比较正规的写法
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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());
3.json写法
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var Circle={
"PI":3.14159,"area":function(r){
return this.PI * r * r;
}
};
alert( Circle.area(1.0) );
4.有点变化，但是实质和第一种一样
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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())
Circle.PI = 3.14159; 能够放入属性中写成this.PI=3.14159;
常用为第一种和第三种
第三种写法的扩展小实例
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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();
