此处let与var区别

Question

var a = 2;(function IIFE(global){    var a =3    console.log(a)//3    console.log(global.a)//2})(window);console.log(a);//2let a = 2;(function IIFE(global){    var a =3    console.log(a)//3    console.log(global.a)//undefine   为什么变成undefined})(window);console.log(a);//2

Answer 1

let const即便在全局环境中定义变量也不会绑定到window对象上
可以找本基础的书看看