javascript - 使用reduce删除对象中的偶数

Question

我得到了一组数字。我创建了一个名为 counts 的对象，其键是数字，值是这些数字在数组中出现的次数。无法弄清楚如何使用 reduce 删除数字的偶数。

A =  [ 20, 1, -1, 2, -2, 3, 3, 5, 5, 1, 2, 4, 20, 4, -1, -2, 5 ]

n =  5

function findOdd(A) {

  let counts = {};

  for (let i = 0; i < A.length; i++) {
    let num = A[i];
    counts[num] = counts[num] ? counts[num] + 1 : 1;
  }

//counts -> { '1': 2, '2': 2, '3': 2, '4': 2, '5': 3, '20': 2, '-1': 2, '-2': 2 }

  const answer = Object.keys(counts).reduce((object, key) => {
    if (key % 2 !== 0) {
      object[key] = counts[key];
    }
    return object;
  }, {})

  return answer;

必须返回奇数的 key 。

解决方案:

function findOdd(A) {
  const counts = {};
  for (let i = 0; i < A.length; i++) {
    let num = A[i];
    counts[num] = counts[num] ? counts[num] + 1 : 1;
  }
  Object.keys(counts).forEach(key => {
    if(counts[key] % 2 === 0) {
    delete counts[key];
    }
  });
  return Number(Object.keys(counts));
}

Answer 1

您可以使用Object.entries 获取整体，然后过滤 值为奇数的条目，然后使用Object 从这些条目重建新的Object .fromEntries:

const countObject = { '1': 2, '2': 2, '3': 2, '4': 2, '5': 3, '20': 2, '-1': 2, '-2': 2 };
const oddEntries = Object.entries(countObject).filter(([key, value]) => value % 2 !== 0);
const oddCountObject = Object.fromEntries(oddEntries)

console.log(oddCountObject)