// 数组去重    let arr = [1, 1, 2, 3];    let unique = [... new Set(arr)];    let a = new Set([1, 2, 3]);    let b = new Set([4, 3, 2]);        // 并集    let union = [...new Set([...a, ...b])];        // 交集    let intersect = [...new Set([...a].filter(x => b.has(x)))];        // 差集    let difference = Array.from(new Set([...a].filter(x => !b.has(x))));