JS 作用域习题

var num1 = 1;
function fun1 (num1){
    console.log(num1);
    num1 = 2;
    console.log(num1);
}
fun1();//undefined,2  未传递参数
num1;//1,

var num1 = 1;
function fun1 (){
    console.log(num1);num1 = 2;console.log(num1);
}
fun1();//1，2  访问全局变量
num1;//2  num1被改变

var num1 = 1;
function fun1 (){
    console.log(num1); var num1 = 2;console.log(num1);
}
fun1();//undefined,2  函数内作用域，尚未赋值
num1;//1 全局num1不改变

var num1 = 1;
function fun1 (){
    console.log(num1); let num1 = 2;console.log(num1);
}
fun1();//报错，暂时性死区，let不提升