一、找出相同元素

（1）方法一

const filterArr = (arr1, arr2) => {
  let result = [];
  for (let i = 0; i < arr1.length; i++) {
    for (let j = 0; j < arr2.length; j++) {
      if (arr1[i] === arr2[j]) {
        result.push(arr1[i]);
      }
    }
  }
  return result;
};

（2）方法二

const filterArr = (arr1, arr2) => {
  return arr1.filter((t) => {
    return arr2.includes(t);
  });
};

（3）方法三

const filterArr = (arr1, arr2) => {
  return arr1.filter((t) => {
    return arr2.indexOf(t) !== -1;
  });
};

一、找出不同元素

（1）方法一

const filterArr = (arr1, arr2) => {
  const arr = [...arr1, ...arr2];
  const newArr = arr.filter((t) => {
    return !(arr1.includes(t) && arr2.includes(t));
  });
  return newArr;
};

（2）方法二

const filterArr2 = (arr1, arr2) => {
  return arr1.concat(arr2).filter((t, i, arr) => {
    return arr.indexOf(t) === arr.lastIndexOf(t);
  });
};

（3）方法三

const arr1 = A.filter((t) => !B.includes(t));
const arr2 = B.filter((x) => !A.includes(x));
const newArr = arr1.concat(arr2);