javascript闭包啊

1

var a = function () {    var id = 0;     function b() {        console.log(id++);    }    b();}a();a();

打印

00

2

var a = function () {    var id = 0;    return function() {        return id++    };}();console.log(a());console.log(a());console.log(a());console.log(a());

打印

0123