两种常见JS面向象写法

基于构造函数

function Circle(r) {
    this.r = r;
}
Circle.PI = 3.14159;
Circle.prototype.area = function() {
    return Circle.PI * this.r * this.r;
}

调用

var c = new Circle(1.0);
console.log(c.area())//3.14159;

类Json写法

var Circle={
    "PI":3.14159,
    "area":function(r){
        return this.PI * r * r;
    }
}; 

调用

console.log(Circle.area(1.0));//3.14159