闭包实现属性私有化

function AA(p,pr){
            var pr = pr==undefined?12:pr;
            this.p=p;
            this.setp=function(){
                this.p=pr;
            }
            this.changePr=function(t){
                pr=t;
            }
            this.sayPr=function(){
                console.log(pr);
            }
        }