两个数组的并集、交集、差集

const arr1 = [1,2,3];

const arr2 = [3,4,5];

// 并集

const union = Array.from(new Set([...arr1,...arr2]));    // union = [1,2,3,4,5]

// 交集

const intersection = Array.from(new Set([...arr1].filter(x => new Set(arr2).has(x))));   // intersection = [3]

// 差集

const difference1 = Array.from(new Set([...arr1].filter(x => !new Set(arr2).has(x))));    // difference1 = [1,2]

const difference2 = Array.from(new Set([...arr2].filter(x => !new Set(arr1).has(x))));    // difference2 = [4,5]