javascript私有静态成员

//构造函数
var Gadget = (function(){

//静态变量/属性
var counter = 0,
    NewGadGet;
    NewGadget = function(){
        counter++;
    }
    NewGadget.prototype.getLastId = function(){
        return counter;
    }
    return NewGadget;

}())

var iphone = new Gadget();
console.log( iphone.getLastId() ); //输出1

var iPad = new Gadget();
console.log( iPad.getLastId() ); //输出2

var iPod = new Gadget();
console.log( iPod.getLastId() ); //输出3