for in 和 for of的区别

for in 和 for of的区别是：in 是遍历对象，of是遍历值

let set = new Set(['red', 'green', 'blue']);
for (let x of set) {
  console.log(x);
}
red
green
blue

let set = new Set(['red', 'green', 'blue']);
for (let x in set) {
  console.log(x);
}
undefined