如何在javascript对象列表中通过键值去重？

Question

考虑以下数组：

[
  { url: "https://url.com/file1", md5: "fbbbabcc19264ce7b376ce4c726b9b85" },
  { url: "https://url.com/file2", md5: "d920d140432b961f07695ec34bd2a8ad" },
  { url: "https://url.com/file3", md5: "fbbbabcc19264ce7b376ce4c726b9b85" },
  { url: "https://url.com/file4", md5: "bf80655dbe90123324f88a778efa39f7" },
  { url: "https://url.com/file5", md5: "fbbbabcc19264ce7b376ce4c726b9b85" }
];

文件"file1“、"file3”和"file5“具有相同的内容，因此具有相同的md5。我只想保留具有不同md5s (file1、file2、file4)的文件。

使用现代ES6实现这一目标的可能方法是什么？

Answer 1

您可以使用reduce来解决这个问题：

​

const list = [
    { url: 'https://url.com/file1', md5: 'fbbbabcc19264ce7b376ce4c726b9b85' },
    { url: 'https://url.com/file2', md5: 'd920d140432b961f07695ec34bd2a8ad' },
    { url: 'https://url.com/file3', md5: 'fbbbabcc19264ce7b376ce4c726b9b85' },
    { url: 'https://url.com/file4', md5: 'bf80655dbe90123324f88a778efa39f7' },
    { url: 'https://url.com/file5', md5: 'fbbbabcc19264ce7b376ce4c726b9b85' },
];

const removeDup = (arr, key) => {
    return arr.reduce((acc, cur) => {
        if (acc.some(a => a[key] === cur[key])) return acc;
        return acc.concat(cur)
    }, [])
};

console.log(removeDup(list, 'md5'))

​

Answer 2

​

const arr = [
        {url: 'https://url.com/file1', md5: 'fbbbabcc19264ce7b376ce4c726b9b85'},
        {url: 'https://url.com/file2', md5: 'd920d140432b961f07695ec34bd2a8ad'},
        {url: 'https://url.com/file3', md5: 'fbbbabcc19264ce7b376ce4c726b9b85'},
        {url: 'https://url.com/file4', md5: 'bf80655dbe90123324f88a778efa39f7'},
        {url: 'https://url.com/file5', md5: 'fbbbabcc19264ce7b376ce4c726b9b85'}
];


const removeDuplicates = (myArr, prop) => {
    return myArr.filter((obj, pos, arr) => {
        return arr.map(mapObj => mapObj[prop]).indexOf(obj[prop]) === pos;
    });
}
const result = removeDuplicates(arr, 'md5');
console.log(result)

​

你可以通过一个特定的键来过滤你的数组，在你的例子中是'md5‘。

Answer 3

您可以使用Set来跟踪已找到的文件。

​

const arr = [{
    url: 'https://url.com/file1',
    md5: 'fbbbabcc19264ce7b376ce4c726b9b85'
  },
  {
    url: 'https://url.com/file2',
    md5: 'd920d140432b961f07695ec34bd2a8ad'
  },
  {
    url: 'https://url.com/file3',
    md5: 'fbbbabcc19264ce7b376ce4c726b9b85'
  },
  {
    url: 'https://url.com/file4',
    md5: 'bf80655dbe90123324f88a778efa39f7'
  },
  {
    url: 'https://url.com/file5',
    md5: 'fbbbabcc19264ce7b376ce4c726b9b85'
  }
]

const uniqueFiles = new Set();
const ans = arr.filter(ele => {
  if (!uniqueFiles.has(ele.md5)) {
    uniqueFiles.add(ele.md5);
    return true;
  }
  return false;
});

console.log(ans)

​