JavaScript中基于日期字段去重：保留最新日期的重复ID元素

Got it, let's tackle this problem where we need to filter an array of objects, keeping only the one with the most recent date for each unique id. Here's a straightforward, efficient way to do it:

Step-by-Step Approach #

• Use a temporary object to track the latest entry for each id — this lets us look up existing entries in constant time.
• Iterate over each item in the input array:
  • For each item, check if we already have an entry for its id in our temporary object.
  • If we don't, add it immediately.
  • If we do, compare the dates: keep the one with the later (more recent) date.
• Finally, convert the values of our temporary object back into an array — that's our filtered result.

Implementation Code #

function filterLatestById(items) {
  const latestMap = {};

  items.forEach(item => {
    const existing = latestMap[item.id];
    // Compare dates directly (YYYY-MM-DD HH:mm:ss strings follow lex order that matches time order)
    if (!existing || item.date > existing.date) {
      latestMap[item.id] = item;
    }
  });

  // Convert the map values to a final array
  return Object.values(latestMap);
}

// Test with your sample array
let myList = [
  { id: "e9519e95-5a10-4274-ac24-de72ad60ffd7", date: "2018-02-21 21:04:13" },
  { id: "026e7ecf-d236-4aff-b26d-7546ac85b7d5", date: "2018-02-22 21:04:13" },
  { id: "e9519e95-5a10-4274-ac24-de72ad60ffd7", date: "2018-02-23 21:04:13" }
];

const filteredList = filterLatestById(myList);
console.log(filteredList);

Output Explanation #

Running this code will return the following array (formatted for readability):

[
  { id: "e9519e95-5a10-4274-ac24-de72ad60ffd7", date: "2018-02-23 21:04:13" },
  { id: "026e7ecf-d236-4aff-b26d-7546ac85b7d5", date: "2018-02-22 21:04:13" }
]

• The duplicate id "e9519e95-5a10-4274-ac24-de72ad60ffd7" is filtered down to the entry with the latest date (2018-02-23).
• The unique id entry is kept as-is.

Notes #

• If you want to be extra safe with date comparisons (in case of non-standard date strings), convert the date strings to Date objects before comparing:

  if (!existing || new Date(item.date) > new Date(existing.date)) {
    latestMap[item.id] = item;
  }
  

• This approach runs in O(n) time complexity, where n is the number of items in the input array — very efficient even for large datasets.

内容的提问来源于stack exchange，提问作者steve-o