Finding highest value(s) amongst JavaScript variables

Question

I'm working on a JS-based game where I'm tracking the scores of several users. At the end of the game, I need to declare a winner. There may be ties.

So, two examples:

player1 = 3
player2 = 5
player3 = 4

(Player 2 is the winner)

player1 = 4
player2 = 2
player3 = 4

(player 1 and 3 tie)

With only 3 players, I could probably just do this with a bunch of nested if/elses comparing each value to each other, but was wondering if there is a more elegant way to go about this...especially in situations where you may have 10 players as an example, where if/else comparisons would get unwieldy pretty fast.

One option seems to be to stick the values in an array, then sort it, but that doesn't give you the variable name--just the values. I could then do a multi-dimensional array, but then things seem to be getting messy again at that point.

Answer 1

There is no easy way to iterate through variable names like player1, player2, etc... without using eval() or requiring those variables to be global variables which is generally a bad way to go.

If they were global variables, you could use this hack, but I would suggest my second method below which stores player info as an array of objects. Here's a hack using global variables (not recommended, but a more direct answer to your question):

// these must be global variables
var score1 = 100;
var score2= 99;
var score3= 80;

function findHighScore() {

    var highestScore = score1;
    var highestScorePlayerNum = 1;
    var tempScore;

    for var (i = 2; i <= 3; i++) {
        // this works only because the score variables are global variables which
        // can be accessed as properties off the window object
        tempScore = window["score" + i];
        if (tempScore > highestScore) {
            highestScore = tempScore;
            highestScorePlayerNum = i;
        }
    }
    return {score: highestScore, playerNum: highestScorePlayerNum};
}

A much better way would involve not keeping each player's score in its own javascript variable, but rather putting it into an array of objects like this:

var playerData = [
    {name: "John", highScore: 145, lastPlayed: 23089234},
    [name: "Bill", highScore: 99, lastPlayed: 59383945}
];

Then, you can loop through the player data, find the highest score and have the name of that player too.

function findHighScore() {
    var highScoreSoFar = 0;
    var result;
    for (var i = 0; i < playerData.length; i++) {
        if (playerData[i].highScore > highScoreSoFar) {
            result = playerDatra[i];
            highScoreSoFar = playerData[i].highScore;
        }
    }
    return result;
}

var highPlayer = findHighScore();
alert("Highest scoring player is " + highPlayer.name + " with a score of " + highPlayer.highScore);

---

If you want to return all players tied for the highest score, you can return an array of players that had the highest score:

function findHighScore() {
    var highScoreSoFar = 0;
    var result = [];
    for (var i = 0; i < playerData.length; i++) {
        if (playerData[i].highScore > highScoreSoFar) {
            // new high score so start a new array with this player in it
            result = [playerData[i]];
            highScoreSoFar = playerData[i].highScore;
        } else if (playerData[i].highScore === highScoreSoFar) {
            // more than one player with this highScore so add this one to the array
            result.push(playerData[i]);
        }
    }
    return result;
}

Answer 2

var players = {
    player1: 3,
    player2: 5,
    player3: 4
};

var sorted = Object.keys(players)
                   .sort(function(keya, keyb) {
                       return players[keyb] - players[keya];
                   })
                   .forEach(function(key) {
                       console.log(key, players[key]);
                   })

DEMO: http://jsfiddle.net/WUAhS/

player2 5

player3 4

player1 3

---

Or use .reduce() if all you want is the high score.

var high_key = Object.keys(players)
                     .reduce(function(keya, keyb) {
                         return players[keya] > players[keyb] ? keya : keyb;
                     });