function a(x,y){
 y = function(){x=2;};
 return function(){
 var x = 3;
 y();
 console.log(x);
 }.apply(this,arguments);
}
a();
//求最后的输出
//题目来自
//https://gist.github.com/ruanyf/cae49b92b0bd43c4d57d