Javascript - 删除 map 中最旧的元素(对象)

Question

我有一个对象:

let lastPosts = {
  id1: {
    date: new Date("10/10/2000 11:30:34"),
  },
  id2: {
    date: new Date("10/10/2000 10:00:00"),
  },
  id3: {
    date: new Date("10/10/2000 10:01:30"),
  },
  id4: {
    date: new Date("11/10/2000 13:09:30"),
  },
  id5: {
    date: new Date("8/10/2005 18:10:15"),
  },
  id6: {
    date: new Date("11/10/2000 10:00:11"),
  },
  id7: {
    date: new Date("10/10/2000 10:00:01"),
  },
  id8: {
    date: new Date("15/10/2000 11:30:34"),
  },
  id9: {
    date: new Date("7/10/2002 11:30:34"),
  },
  id10: {
    date: new Date("8/10/2005 18:10:14"),
  },
  id11: {
    date: new Date("11/10/2000 10:00:00"),
  },
};

我需要确保“lastPosts”仅包含 9 个帖子(元素)，删除剩余的最旧的帖子。

function deleteOldestLastPosts(lastPosts) {
    if (Object.keys(lastPosts).length > 9) {
       // What can I do here?
    }
}

所以，我得到以下结果:

{
  id1: {
    date: new Date("10/10/2000 11:30:34"),
  },
  id3: {
    date: new Date("10/10/2000 10:01:30"),
  },
  id4: {
    date: new Date("11/10/2000 13:09:30"),
  },
  id5: {
    date: new Date("8/10/2005 18:10:15"),
  },
  id6: {
    date: new Date("11/10/2000 10:00:11"),
  },
  id8: {
    date: new Date("15/10/2000 11:30:34"),
  },
  id9: {
    date: new Date("7/10/2002 11:30:34"),
  },
  id10: {
    date: new Date("8/10/2005 18:10:14"),
  },
  id11: {
    date: new Date("11/10/2000 10:00:00"),
  },
}

有什么想法吗？

Answer 1

按日期对所有值进行排序。从此排序数组中删除最新的 9 个元素，生成要删除的日期数组。然后循环遍历属性，如果它在数组中则将其删除。

function deleteOldestLastPosts(lastPosts) {
  let values = Object.values(lastPosts);
  if (values.length > 9) {
    let datesToDelete = values.map(el => el.date).sort((a, b) => a - b);
    datesToDelete.splice(-9);
    Object.entries(lastPosts).forEach(([key, {
      date
    }]) => {
      if (datesToDelete.includes(date)) {
        delete lastPosts[key];
      }
    });
  }
}

let lastPosts = {
  id1: {
    date: new Date("10/10/2000 11:30:34"),
  },
  id2: {
    date: new Date("10/10/2000 10:00:00"),
  },
  id3: {
    date: new Date("10/10/2000 10:01:30"),
  },
  id4: {
    date: new Date("11/10/2000 13:09:30"),
  },
  id5: {
    date: new Date("8/10/2005 18:10:15"),
  },
  id6: {
    date: new Date("11/10/2000 10:00:11"),
  },
  id7: {
    date: new Date("10/10/2000 10:00:01"),
  },
  id8: {
    date: new Date("15/10/2000 11:30:34"),
  },
  id9: {
    date: new Date("7/10/2002 11:30:34"),
  },
  id10: {
    date: new Date("8/10/2005 18:10:14"),
  },
  id11: {
    date: new Date("11/10/2000 10:00:00"),
  },
};

deleteOldestLastPosts(lastPosts);
console.log(lastPosts);