Javascript Create Leaderboard Object Based on Score Requirements

denistepp
March 24, 2023
155 views
1 vote
2 Answers

I have two objects in javascript:

Users:

      { userId: 'id1', score: 100 },
      { userId: 'id2', score: 3 },
      { userId: 'id3', score: 2 },
      { userId: 'id4', score: 1 }

and minimumRequirements:

 { firstPlaceMinScore: 100, secondPlaceMinScore: 50, thirdPlaceMinScore: 10 }

I am trying to create a leaderboard where users should be sorted by their places if they met the requiremenents for minimum points. For example

Group1:

      { userId: 'id1', score: 3 },
      { userId: 'id2', score: 2 },
      { userId: 'id3', score: 1 }

should return:

      { userId: 'id1', place: 4 },
      { userId: 'id2', place: 5 },
      { userId: 'id3', place: 6 }

group2:

      { userId: 'id1', score: 55 },
      { userId: 'id2', score: 30 },
      { userId: 'id3', score: 52 },
      { userId: 'id4', score: 10 },
      { userId: 'id5', score: 1 }

should return:

      { userId: 'id1', place: 2 },
      { userId: 'id3', place: 3 },
      { userId: 'id2', place: 4 },
      { userId: 'id4', place: 5 },
      { userId: 'id5', place: 6 }

I have written the following function but i can’t get around the filtering of leaders part, they are messing up the count:

function getLeaderboard(users, minScores) {
    let leaderboard = [];
    let formattedMinScores = Object.values(minScores);

    const sortedUsers = users.sort((a, b) => b.score - a.score);

    loop1: for (let i = 0; i < sortedUsers.length; i++) {
      let currentPlace = i + 1;
      loop2: for (let j = 0; j < formattedMinScores.length; j++) {
        ++currentPlace;
        if (sortedUsers[i].score >= formattedMinScores[j]) {
          
          currentPlace = j + 1;
          break loop2;
        }
      }
      leaderboard.push({
        place: currentPlace,
        userId: sortedUsers[i].userId
      });
    }

    console.log(leaderboard);
    return leaderboard;
  }

Tags: javascript

Answers

Here is a solution: you start at place 0 and for each user, you increment the place by 1. You also increment it by the number of minimum required scores that are above the user’s score (s > user.score), as long as those minimum score are not for a place above the current place (i+1 >= currentPlace)

let group1 = [
    { userId: 'id1', score: 55 },
    { userId: 'id2', score: 30 },
    { userId: 'id3', score: 52 },
    { userId: 'id4', score: 10 },
    { userId: 'id5', score: 1 }
]

let group2 = [
    { userId: 'id1', score: 3 },
    { userId: 'id2', score: 2 },
    { userId: 'id3', score: 1 }
]

let minScores = { firstPlaceMinScore: 100, secondPlaceMinScore: 50, thirdPlaceMinScore: 10 }

function getLeaderboard(users, minScores) {
    let leaderboard = [];
    let formattedMinScores = Object.values(minScores);
    const sortedUsers = users.sort((a, b) => b.score - a.score);

    let currentPlace = 0
    for (let user of sortedUsers) {
        currentPlace += 1 + formattedMinScores.filter((s, i) => s > user.score && i+1 >= currentPlace).length; 
        leaderboard.push({
            place: currentPlace,
            userId: user.userId
        });
    }

    console.log(leaderboard);
    return leaderboard;
}

getLeaderboard(group1, minScores)
getLeaderboard(group2, minScores)

You can sort the scores first then iterate through the positional mins.

Note: I changed your placement min object into an indexable array.

const minScores = [100, 50, 10];

const leaderboardPositions = (group) => {
  const sorted = group
    .map(({ userId, score }, index) => ({ userId, score, index }))
    .sort((a, b) => b.score - a.score || a.index - b.index);
  let scoreIndex = 0;
  for (let i = 0; i < sorted.length; i++) {
    const player = sorted[i];
    while (player.score < minScores[scoreIndex] && scoreIndex < minScores.length) {
      scoreIndex++;
    }
    player.place = scoreIndex + 1;
    scoreIndex++;
  }
  return sorted.map(({ userId, place }) => ({ userId, place }));
};

const
  group1 = [
    { userId: 'id1', score: 3 },
    { userId: 'id2', score: 2 },
    { userId: 'id3', score: 1 }
  ],
  group2 = [
    { userId: 'id1', score: 55 },
    { userId: 'id2', score: 30 },
    { userId: 'id3', score: 52 },
    { userId: 'id4', score: 10 },
    { userId: 'id5', score: 1 }
  ];

console.log(leaderboardPositions(group1));
console.log(leaderboardPositions(group2));

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