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我必须按艺术家对这个 JSON 进行分组，并获得每个艺术家的总听众总数。完成此操作后，我需要找到听得最多的艺术家并展示歌曲。什么是最有效的方法？我已经尝试了几种方法，但无法得到它。有没有 JS 函数可以做到这一点？

这是 JSON：

[
    {
        "name": "The Less I Know the Better",
        "duration": "0",
        "listeners": "439958",
        "mbid": "",
        "url": "https://www.last.fm/music/Tame+Impala/_/The+Less+I+Know+the+Better",
        "artist": {
            "name": "Tame Impala",
            "mbid": "63aa26c3-d59b-4da4-84ac-716b54f1ef4d",
            "url": "https://www.last.fm/music/Tame+Impala"
        },
        "@attr": {
            "rank": "0"
        },
        "genre": "reggae"
    },
    {
        "name": "Creep",
        "duration": "239",
        "listeners": "1647583",
        "mbid": "d11fcceb-dfc5-4d19-b45d-f4e8f6d3eaa6",
        "url": "https://www.last.fm/music/Radiohead/_/Creep",
        "artist": {
            "name": "Radiohead",
            "mbid": "a74b1b7f-71a5-4011-9441-d0b5e4122711",
            "url": "https://www.last.fm/music/Radiohead"
        },
        "@attr": {
            "rank": "1"
        },
        "genre": "jazz"
    }
]

这个 JSON 文件是一个例子，真正的有 800 多行。我试过做一个艺术家列表，但我不能总结每个艺术家每首歌的听众总数。

4

2 回答 2

1

像这样的东西？

const json = `
[{
        "name": "The Less I Know the Better",
        "duration": "0",
        "listeners": "439958",
        "mbid": "",
        "url": "https://www.last.fm/music/Tame+Impala/_/The+Less+I+Know+the+Better",
        "artist": {
            "name": "Tame Impala",
            "mbid": "63aa26c3-d59b-4da4-84ac-716b54f1ef4d",
            "url": "https://www.last.fm/music/Tame+Impala"
        },
        "@attr": {
            "rank": "0"
        },
        "genre": "reggae"
    },
    {
        "name": "Creep",
        "duration": "239",
        "listeners": "1647583",
        "mbid": "d11fcceb-dfc5-4d19-b45d-f4e8f6d3eaa6",
        "url": "https://www.last.fm/music/Radiohead/_/Creep",
        "artist": {
            "name": "Radiohead",
            "mbid": "a74b1b7f-71a5-4011-9441-d0b5e4122711",
            "url": "https://www.last.fm/music/Radiohead"
        },
        "@attr": {
            "rank": "1"
        },
        "genre": "jazz"
    },
    {
        "name": "Other song of Radiohead for example",
        "duration": "239",
        "listeners": "1647583",
        "mbid": "d11fcceb-dfc5-4d19-b45d-f4e8f6d3eaa6",
        "url": "https://www.last.fm/music/Radiohead/_/Creep",
        "artist": {
            "name": "Radiohead",
            "mbid": "a74b1b7f-71a5-4011-9441-d0b5e4122711",
            "url": "https://www.last.fm/music/Radiohead"
        },
        "@attr": {
            "rank": "1"
        },
        "genre": "jazz"
    }
]`

const artists = {};
for (const song of JSON.parse(json)) {
    if (artists[song.artist.name]) {
    artists[song.artist.name].listeners += parseInt(song.listeners, 10);
    artists[song.artist.name].songs.push(song.name);
  } else {
    artists[song.artist.name] = {
      listeners: parseInt(song.listeners, 10),
      songs: [song.name],
    };
  }
}
console.log(artists);

于 2020-11-01T22:01:10.240 回答
1

您可以reduce()将数组放入 aMap中，这使得累积重复项变得简单。您也可以只对听众进行统计，从而避免第二次迭代。

结果是一个Map形状：

{
  "Artist1": {
    "songs": [
      {...},
      {...}
    ]
    "listeners": 0
  },
  "Artist2": {
    "songs": [
      {...},
      {...}
    ]
    "listeners": 0
  }
  ...
}


const songs = [
    {
        "name": "The Less I Know the Better",
        "duration": "0",
        "listeners": "439958",
        "mbid": "",
        "url": "https://www.last.fm/music/Tame+Impala/_/The+Less+I+Know+the+Better",
        "artist": {
            "name": "Tame Impala",
            "mbid": "63aa26c3-d59b-4da4-84ac-716b54f1ef4d",
            "url": "https://www.last.fm/music/Tame+Impala"
        },
        "@attr": {
            "rank": "0"
        },
        "genre": "reggae"
    },
    {
        "name": "Creep",
        "duration": "239",
        "listeners": "1647583",
        "mbid": "d11fcceb-dfc5-4d19-b45d-f4e8f6d3eaa6",
        "url": "https://www.last.fm/music/Radiohead/_/Creep",
        "artist": {
            "name": "Radiohead",
            "mbid": "a74b1b7f-71a5-4011-9441-d0b5e4122711",
            "url": "https://www.last.fm/music/Radiohead"
        },
        "@attr": {
            "rank": "1"
        },
        "genre": "jazz"
    },
    {
        "name": "Go to Sleep",
        "duration": "239",
        "listeners": "16583",
        "mbid": "d11fcceb-dfc5-4d19-b45d-f4e8f6d3eaa6",
        "url": "https://www.last.fm/music/Radiohead/_/Go to Sleep",
        "artist": {
            "name": "Radiohead",
            "mbid": "a74b1b7f-71a5-4011-9441-d0b5e4122711",
            "url": "https://www.last.fm/music/Radiohead"
        },
        "@attr": {
            "rank": "3"
        },
        "genre": "jazz"
    }
]

const byArtist = songs.reduce((acc, song) => {
  const artistName = song.artist.name;
  const match = acc.get(artistName);
  if (match) {
    match.songs.push({...song});
    match.listeners += parseInt(song.listeners);
  } else {
    acc.set(artistName, {songs: [{...song}], listeners: +song.listeners});
  }
  return acc;
}, new Map);

console.log(Object.fromEntries(byArtist));

解释

您可以继续阅读Map并reduce()进一步了解。

const byArtist = songs.reduce((acc, song) => {
  // get the artist name from the current song object
  const artistName = song.artist.name;
  // try to get the element referenced by artistName,
  // returns undefined if we haven't added that artist yet
  // otherwise it returns the object holding "songs" and "listeners"
  const match = acc.get(artistName);
  if (match) {
    // if match is truthy (successfully retrieved an entry)
    // push a copy of the song into the "songs" array
    match.songs.push({...song});
    // increment the listener count by the songs listeners
    match.listeners += parseInt(song.listeners);
  } else {
    // else set a new key: value pair useing artistName as the key
    // and creating a new object contianing "songs" and "listeners"
    acc.set(artistName, {songs: [{...song}], listeners: +song.listeners});
  }
  // return the mutated accumulator for the next iteration to use.
  return acc;
}, new Map); // this initializes the accumulator as a new Map object

// creates an Object from the Map so that it can be logged easily
console.log(Object.fromEntries(byArtist));
于 2020-11-01T22:04:39.957 回答