ES6 scope(scope)

Scope:
1.Global scope(global) 2.Function scope(function)

Global scope

var a=1;
console.log(a);//1
    //{}表示语句块
    
if(a==1){
    var b=2;
    console.log(b);//2
}
console.log(b);

for (var c = 0; c < 10; c++) {
    ;
};
    console.log(c);

function fn(){
    var d=3;
    console.log(d);
}
fn();
//console.log(d);//报错

console.log("---window---");
console.log(a);//1
console.log(b);//2
console.log(c);//10
console.log(d);//报错

//全局变量 挂载在window对象的属性。

//声明变量有前置功能(hosting hot)

//函数也有前置功能

console.log(c);
var c;//undefined

Function scope

var a=1;
function fn(){
    console.log(a);//1
    /*console.log(a);//undefined
    var a=2;*/
}
fn();

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