数组的交集并集和差级

let arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9];
let arr2 = [1, 3, 5, 7, 9];

// 交集
let arr3 = arr1.filter((item) => {
  return arr2.includes(item);
});
console.log(arr3);

// 并集
let arr4 = arr1.concat(arr2);
console.log(arr4);
// 并集
console.log(Array.from(new Set([...arr1, ...arr2])));

// 差集
let arr5 = arr1.filter((item) => {
  return !arr2.includes(item);
});
console.log(arr5);