当前位置：首页 > 编程 > 正文

var 与let 的区别

{
    var a = 'hello'   // 函数作业域
    let b = 'world'   // 块级作用域
}


console.log(a)
console.log(b)  //b is not defined 

变量提升:

var a = 'hello'

function func(){
    a = 'world'
}

func()

console.log(a) //world

let a = 'hello'

function func(){
    a = 'world'
}


console.log(a)  // hello

let a = 'hello'   
let a = 'world'   // 报错

var a = 'hello'
var b = 'world'  // 不报错