js 函数定义域

1、1

let a = 1;function fun () {console.log(a)
}function fun1 () {let a = 2;fun();
}fun1();

2、2

let a = 1;function fun1 () {let a = 2;function fun () {console.log(a)}fun();
}fun1();

3、2

let a = 1;function fun1() {function fun() {console.log(a);}let a = 2;fun();
}fun1();

4、ReferenceError: Cannot access 'a' before initialization

let a = 1;function fun1() {function fun() {console.log(a);}fun();let a = 2;}fun1();