如何求和对象数组中 javascript 数组的属性之和？

Question

I'm making a game where each player can submit an answer on a given question and other players can vote on an answer of another player. I store these results in an array of game rounds which may look something like the following:

const roundHistory = [
  {
    question: 'question1',
    submissions: [
      {
        explanation: 'answer1',
        player: { id: 'id1', name: 'player1' },
        votes: [
          { id: 'id2', name: 'player2' },
          { id: 'id3', name: 'player3' },
        ],
      },
      {
        explanation: 'answer2',
        player: { id: 'id2', name: 'player2' },
        votes: [{ id: 'id1', name: 'player1' }],
      },
      {
        explanation: 'answer3',
        player: { id: 'id3', name: 'player3' },
        votes: [],
      },
    ],
  },
  {
    question: 'question2',
    submissions: [
      {
        explanation: 'answer1',
        player: { id: 'id1', name: 'player1' },
        votes: [
          { id: 'id2', name: 'player2' },
          { id: 'id3', name: 'player3' },
        ],
      },
      {
        explanation: 'answer2',
        player: { id: 'id2', name: 'player2' },
        votes: [{ id: 'id1', name: 'player1' }],
      },
      {
        explanation: 'answer3',
        player: { id: 'id3', name: 'player3' },
        votes: [],
      },
    ],
  },
];

As you can see there are 3 players in the game since each round (index of the roundHistory array) has 3 submissions. Each submission has a property player which represents the player who submitted the submission. And then each submission has a property votes which is an array of the players who voted for that submission. Now my question:

How can I get the total received votes per player of all rounds?

---

What I've tried so far... I thought, first I'd get the total received votes per player per round like so:

 const roundHistory = [{question:'question1',submissions:[{explanation:'answer1',player:{id:'id1',name:'player1'},votes:[{id:'id2',name:'player2'},{id:'id3',name:'player3'},],},{explanation:'answer2',player:{id:'id2',name:'player2'},votes:[{id:'id1',name:'player1'}],},{explanation:'answer3',player:{id:'id3',name:'player3'},votes:[],},],},{question:'question2',submissions:[{explanation:'answer1',player:{id:'id1',name:'player1'},votes:[{id:'id2',name:'player2'},{id:'id3',name:'player3'},],},{explanation:'answer2',player:{id:'id2',name:'player2'},votes:[{id:'id1',name:'player1'}],},{explanation:'answer3',player:{id:'id3',name:'player3'},votes:[],},],},]; const getTotalReceivedVotesPerPlayerInRound = (round) => { return roundHistory[round].submissions.map((s) => ({ player: s.player, totalVotes: s.votes.length, })); } console.log(getTotalReceivedVotesPerPlayerInRound(0));

But I got stuck at adding all results of all rounds together. Note that I tried to simplify all used objects such as a player. In my application these are mostly classes for which I have several utility methods. One of them is the getTotalReceivedVotesPerPlayerInRound() method that I can use on a round (index of the roundHistory array).

I expect the final result to be of the same shape as the result of my already written function: An array of objects with two properties: player (the player object) and totalVotes . E. g.:

const result = [
  {
    "player": {
      "id": "id1",
      "name": "player1"
    },
    "totalVotes": 2
  },
  {
    "player": {
      "id": "id2",
      "name": "player2"
    },
    "totalVotes": 1
  },
  {
    "player": {
      "id": "id3",
      "name": "player3"
    },
    "totalVotes": 0
  }
];

Answer 1

Presented below is one possible way to achieve the desired objective.

Code Snippet

 const getPlayerTotalVotes = arr => ( Object.values( arr.reduce( (acc, { submissions}) => { submissions.forEach( ({ player: { id, name }, votes }) => { acc[id]??= { player: { id, name }, totalVotes: 0 }; acc[id].totalVotes += votes.length; } ) return acc; }, {} ) ) ); /* explanation of the code method to obtain the total votes per-player for all rounds const getPlayerTotalVotes = arr => ( Object.values( // extract only the values of the below intermediate result object arr.reduce( // ".reduce()" to iterate and sum votes-count (acc, { submissions}) => { // "acc" is the accumulator; destructure iterator // to directly access "submissions" array // then, iterate using ".forEach()" over "submissions" submissions.forEach( // destructure to access "votes" array and the particular player "id" ({ player: { id }, votes }) => { // conditionally-assign 0 if "id" not already present in "acc" acc[id]??= 0; // count the "votes" and add it to the "acc" prop with key as "id" acc[id] += votes.length; } ) return acc; // explicitly return "acc" for each iteration }, {} // "acc" is initialized as an empty object ) // implicit return of the result from ".reduce()" to caller ) ); */ const roundHistory = [{ question: 'question1', submissions: [{ explanation: 'answer1', player: { id: 'id1', name: 'player1' }, votes: [{ id: 'id2', name: 'player2' }, { id: 'id3', name: 'player3' }, ], }, { explanation: 'answer2', player: { id: 'id2', name: 'player2' }, votes: [{ id: 'id1', name: 'player1' }], }, { explanation: 'answer3', player: { id: 'id3', name: 'player3' }, votes: [], }, ], }, { question: 'question2', submissions: [{ explanation: 'answer1', player: { id: 'id1', name: 'player1' }, votes: [{ id: 'id2', name: 'player2' }, { id: 'id3', name: 'player3' }, ], }, { explanation: 'answer2', player: { id: 'id2', name: 'player2' }, votes: [{ id: 'id1', name: 'player1' }], }, { explanation: 'answer3', player: { id: 'id3', name: 'player3' }, votes: [], }, ], }, ]; console.log( 'total votes per player\n', getPlayerTotalVotes(roundHistory) );

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Explanation

Inline comments added to the snippet above.

EDIT Using the given method to obtain sum of votes "per-round"

 const roundHistory = [{question:'question1',submissions:[{explanation:'answer1',player:{id:'id1',name:'player1'},votes:[{id:'id2',name:'player2'},{id:'id3',name:'player3'},],},{explanation:'answer2',player:{id:'id2',name:'player2'},votes:[{id:'id1',name:'player1'}],},{explanation:'answer3',player:{id:'id3',name:'player3'},votes:[],},],},{question:'question2',submissions:[{explanation:'answer1',player:{id:'id1',name:'player1'},votes:[{id:'id2',name:'player2'},{id:'id3',name:'player3'},],},{explanation:'answer2',player:{id:'id2',name:'player2'},votes:[{id:'id1',name:'player1'}],},{explanation:'answer3',player:{id:'id3',name:'player3'},votes:[],},],},]; const getTotalReceivedVotesPerPlayerInRound = (round) => { return roundHistory[round].submissions.map((s) => ({ player: s.player, totalVotes: s.votes.length, })); } const getTotalAllRounds = rh => ( Object.values( rh.reduce( (acc, _, idx) => { getTotalReceivedVotesPerPlayerInRound(idx)?.forEach( ({player: { id, name}, totalVotes}) => { acc[id]??= { player: {id, name}, totalVotes: 0 }; acc[id].totalVotes += totalVotes; } ); return acc; }, {} ) ) ); console.log(getTotalAllRounds(roundHistory));

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