数组交集差集并集

let one = [1, 2, 3, 4, 5];
let two = [2, 3, 4, 7];
const intersection = (a, b) => {
  // a b数组的交集
  let arr = a.filter(v => {
    // b是否包含a的元素，包含就返回true,交集
    return b.includes(v);
  });
  return arr;
};
const difference = (a, b) => {
  // a b 数组的差集
  let arr = [...a, ...b].filter(v => {
    // a和b是否包含v 不包含返回!false  出现有一个不包含(另一个数组就包含 找到差值),就返回true 添加进数组
    return !a.includes(v) || !b.includes(v);
  });
  return arr;
};

const unionArr = (a, b) => {
  return Array.from(new Set([...a, ...b])); // 并集可以理解为合并数组去重,直接用set即可
};
console.log(difference(one, two), intersection(one, two), unionArr(one, two));

function arrSet(a, b, type) {
  let set;
  a = new Set(a);
  b = new Set(b);
  if (type === 'difference') {
    // ab数组差集
    set = new Set([...a, ...b].filter(x => !b.has(x) || !a.has(x)));
  } else if (type === 'intersection') {
    // ab数组交集
    set = new Set([...a].filter(x => b.has(x)));
  } else {
    // ab数组并集
    set = new Set([...a, ...b]);
  }
  return Array.from(set); // 转为set
}
console.log(
  arrSet(one, two, 'difference'),
  arrSet(one, two, 'intersection'),
  arrSet(one, two, 'union')
);