js如何定义集合

let mySet = new Set();
mySet.add(1);
mySet.add(2);
mySet.add(2); // 重复的值不会被添加
console.log(mySet); // Set {1, 2}

let arr = [1, 2, 2, 3, 4, 4, 5];
let mySet = new Set(arr);
console.log(mySet); // Set {1, 2, 3, 4, 5}

let mySet = new Set([1, 2, 3]);
for (let item of mySet) {
  console.log(item);
}
// 输出:
// 1
// 2
// 3

let mySet = new Set([1, 2, 3]);
let arr = Array.from(mySet);
console.log(arr); // [1, 2, 3]

let arr = [...mySet];

let mySet = new Set([1, 2, 3]);
console.log(mySet.has(2)); // true
console.log(mySet.has(4)); // false