JS Count occurrences in array and sort by highest

Question

I'm trying to write a vote counting function, I have an array of objects and each object has a property called currentVote which has a userId value. I want to find out which userID has the most votes. Using lodash this is what I got so far:

function countVotes(players) {
  return new Promise(function(resolve, reject) {
    //votes should be empty, filled it with some sample values
    let votes = ['312139659792875521','360445341989863434', '312139659792875521','360445341989863435','1','9999999999999999999999'];
    for (let i = 0, j = players.length; i < j; i++) {
      votes.push(players[i].currentVote);
    }
    let tally = _.chain(votes)
      .countBy()
      .toPairs()
      .sortBy(1).reverse()
      .map(0)
      .value()[0];
    resolve(tally);
  });

How can I pick a random value IF I have multiple userIds with the same number of votes. At the moment it seems that the smallest ID will always be picked?

Instead of picking the first one, check how many there are with the same number of votes and pick a random one amongst them. — Bergi
– Bergi, Commented Nov 4, 2017 at 16:27

Edison Trutwein · Accepted Answer · 2017-11-04 16:54:53Z

3

Based on your question, I believe your object is as follow, I have used the array method sort to sort the array in descending and picked up the first element. Hope this helps.

let players = [{
                 "userId":1,
                 "currentVotes":2220
               },
               {
                 "userId":2,
                 "currentVotes":383830
               },
               {
                 "userId":3,
                 "currentVotes":6894740
               },
               {
                 "userId":4,
                 "currentVotes":6894740
               },
               {
                 "userId":5,
                 "currentVotes":1
               }
              ];


function getHighestVoteByRandowm(players){

    let arrSameVotes = [];

    let i = 0;
    do{
        arrSameVotes.push(players[i]);
        temp = players[i].currentVotes;
        i++;
    }while(players[i].currentVotes == temp);

    let rndTill = arrSameVotes.length - 1;
    let rndVal = Math.round(Math.random() * rndTill);

    return arrSameVotes[rndVal];

}

function sortVotes(a,b){
    return b.currentVotes - a.currentVotes;
}

let highestVotesPlayer = getHighestVoteByRandowm(players.sort(sortVotes));

console.log(highestVotesPlayer);

edited Nov 4, 2017 at 16:54

answered Nov 4, 2017 at 16:31

Edison Trutwein

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1 Comment

Edison Trutwein Over a year ago

check this out, i have edited the code to get the random value if the votes are same.

ktilcu · Accepted Answer · 2017-11-04 16:23:42Z

1

You could use _.shuffle and _.first. Maybe something like:

_.chain(votes).countBy()
  .groupBy() // added this to get a list of all the ones that have matching vote counts
  .toPairs()
  .sortBy(0)
  .reverse()
  .first() // most votes
  .last() // get the user ids
  .shuffle() // randomize order
  .first() // get whatever is first
  .value()

answered Nov 4, 2017 at 16:23

ktilcu

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