题目

  1. var 重复声明 ```javascript var a = 12 var a = 13 console.log(a)

let a = 12 let a = 13 console.log(a)

fn() function fn () { console.log(1) } fn() function fn () { console.log(2) } fn() var fn = function () { console.log(3) } fn() function fn () { console.log(4) } fn() function fn () { console.log(5) } fn()

console.log(a) if (!(‘a’ in window)) { var a = 13 } console.log(a)

console.log(fn) if (‘fn’ in window) { // fn function fn() { console.log(‘fn’) } } fn() ```