function test(){
let a = 5;
if (true) {
let b = 6;
}
console.log(a); // 5
console.log(b); // 引用错误：b 未定义
}
const a = [1,2,3];
const double = x => x * 2; // 箭头函数
console.log(a.map(double));
var bob = {
_name: "bob",
_friends: [],
printfriends() {
this._friends.foreach(f =>
console.log(this._name " knows " f));
}
};
console.log(bob.printfriends());