JavaScript DRY Up Code, Avoid Repeat Object Key Exist Checks?-CodePudding

Hey there hope all is well,

Just wrapping up a small coding assignment where i'd like to avoid repeating myself in the implementation

let matchScores = [
  {
    '0': { 'Team A': 3, 'Team B': 3 },
    '1': { 'Team D': 1, 'Team F': 0 },
    '2': { 'Team E': 2, 'Team C': 0 }
  },
  {
    '3': { 'Team E': 1, 'Team F': 2 },
    '4': { 'Team B': 0, 'Team D': 0 },
    '5': { 'Team C': 4, 'Team A': 2 }
  }
]

This is the input to the function which is array of objects that have a "match" results between two teams. Each element in the array is a different "day" of games that need to be appended to a total point score. The goal is to create a function that for each "day ill iterate through the array and sum up the points awarded for the winners of the matches.

If a team wins they are awarded 3 points, if there is a tie both teams are only awarded one point.

Expected Output

Match 1
Team A, 3 pts
Team B, 3 pts
Team C, 1 pt

Match 2
Team A, 4 pts
Team B, 3 pts
Team C, 3 pts

function calculateResults(matchDays) {

  let matchScore = {};
  matchDays.forEach((day, i) => {


    for (const [key, value] of Object.entries(day)) {
      let match = Object.entries(value);
      let team1 = match[0];
      let team2 = match[1];

      // team 1 win
      if (team1[1] > team2[1]) {
        // if team's score exists
        if (matchScore[team1[0]]) {
          // add value
          matchScore[team1[0]]  = 3;
        } else {
          // create value
          matchScore[team1[0]] = 3;
        }
      }

      // team 2 win
      if (team1[1] < team2[1]) {
        // if team's score exists
        if (matchScore[team2[0]]) {
          matchScore[team2[0]]  = 3;
        } else {
          matchScore[team2[0]] = 3;
        }
      }
      // tie
      if (team1[1] === team2[1]) {
        if (matchScore[team1[0]]) {
          matchScore[team1[0]]  = 1;
        } else {
          matchScore[team1[0]] = 1;
        }

        if (matchScore[team2[0]]) {
          matchScore[team2[0]]  = 1;
        } else {
          matchScore[team2[0]] = 1;
        }
      }
    }

  });
}

Here's my current implementation. Is there any way I can avoid repeating the object key value checks if it exists? Im currently trying to iterate through and store the value in matchScore

CodePudding user response：

You can use the new(ish) nullish coalescing operator to convert undefined to 0, then just always do the addition:

// team 1 win
if (team1[1] > team2[1]) {
    matchScore[team1[0]] = matchScore[team1[0]] ?? 0   3; // ***
}

// team 2 win
if (team1[1] < team2[1]) {
    matchScore[team2[0]] = matchScore[team2[0]] ?? 0   3; // ***
}

// ...and so on...

?? evaluates its left-hand operand and, if that value is not undefined, takes that value as its result; if the left-hand value is undefined, ?? evaluates its right-hand operand and takes that value as its result.

If you need to target an environment that doesn't have ?? (yet), in this particular case you can use || (logical OR) instead. || does the same thing ?? does, but the check isn't just for undefined, but for any falsy value. In this particular case, that's fine.

You probably want else if and else in there as well:

if (team1[1] > team2[1]) {
    // team 1 win
    matchScore[team1[0]] = matchScore[team1[0]] ?? 0   3;
} else if (team1[1] < team2[1]) {
    // team 2 win
    matchScore[team2[0]] = matchScore[team2[0]] ?? 0   3;
} else {
    // tie
    matchScore[team1[0]] = matchScore[team1[0]] ?? 0   1;
    matchScore[team2[0]] = matchScore[team2[0]] ?? 0   1;
}