Selecting a prize category based on two parameters

Question

I get an object with categories, first category has 2 types. Both types are in the first and second position but sorting is not constant.

I have to return category 1 with playLevel === 2 when bonusPlus is true and category 1 with playLevel === 1 otherwise.

Here is the code:

const getFirstCategory = (bonusPlus, prizeCategories) => {
  if (bonusPlus) {
    if (prizeCategories[0].playLevel === 2) {
      return [prizeCategories[0]];
    }
    return [prizeCategories[1]];
  }
  if (prizeCategories[0].playLevel === 1) {
    return [prizeCategories[0]];
  }
  return [prizeCategories[1]];
};

How can I reduce / beautify this code?

Answer 1

To make @kfx's answer more readable:

const getFirstCategory = (bonusPlus, prizeCategories) => {
  const bonusPlusLevel = bonusPlus ? 2 : 1;
  if (prizeCategories[0].playLevel === bonusPlusLevel) {
    return [prizeCategories[0]];
  }
  return [prizeCategories[1]];
};

Answer 2

Using the ternary operator and an extra variable would allow to reduce the size of the code:

const getFirstCategory = (bonusPlus, prizeCategories) => {
  var index = (prizeCategories[0].playLevel === (bonusPlus ? 2 : 1) ? 0 : 1);
  return [prizeCategories[index]];
};

Answer 3

I would start by leaving the unnecessary condition brackets to make the program flow more obvious :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  if (bonusPlus) {
    if (prizeCategories[0].playLevel === 2) {
      return [prizeCategories[0]];
    } else {
      return [prizeCategories[1]];
    }
  } else {
    if (prizeCategories[0].playLevel === 1) {
      return [prizeCategories[0]];
    } else {
      return [prizeCategories[1]];
    }
  }
};

Then use a variable for the result :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  let firstCategory;
  if (bonusPlus) {
    if (prizeCategories[0].playLevel === 2) {
      firstCategory = [prizeCategories[0]];
    } else {
      firstCategory = [prizeCategories[1]];
    }
  } else {
    if (prizeCategories[0].playLevel === 1) {
      firstCategory = [prizeCategories[0]];
    } else {
      firstCategory = [prizeCategories[1]];
    }
  }
  return firstCategory;
};

Then mutualise the use of [prizeCategories[i]] :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  let index;
  if (bonusPlus) {
    if (prizeCategories[0].playLevel === 2) {
      index = 0;
    } else {
      index = 1;
    }
  } else {
    if (prizeCategories[0].playLevel === 1) {
      index = 0;
    } else {
      index = 1;
    }
  }
  return [prizeCategories[index]];
};

Then mutualise the index double initialisation :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  let lvlToCheck;
  if(bonusPlus) {
      lvlToCheck = 2;
  } else {
      lvlToCheck = 1;
  }
  let index;
  if (prizeCategories[0].playLevel === lvlToCheck) {
    index = 0;
  } else {
    index = 1;
  }
  return [prizeCategories[index]];
};

You can then make the code shorter (but not necessaraly more readable) with a ternary operator :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  const lvlToCheck = bonusPlus ? 2 : 1;
  let index;
  if (prizeCategories[0].playLevel === lvlToCheck) {
    index = 0;
  } else {
    index = 1;
  }
  return [prizeCategories[index]];
};

Or even two :

const getFirstCategory = (bonusPlus, prizeCategories) => {
  const lvlToCheck = bonusPlus ? 2 : 1;
  let index = (prizeCategories[0].playLevel === lvlToCheck) ? 0 : 1;
  return [prizeCategories[index]];
};

You can shorter the code even more but I would stop there (if not before).

Answer 4

You can take advantage of the fact that when adding a boolean to a number, the boolean will be coerced to 0 or 1. That lets you simplify the function down to a single expression:

const getFirstCategory = (bonusPlus, prizeCategories) => [
    prizeCategories[(prizeCategories[0].playLevel === 1 + bonusPlus) ? 0 : 1]
];

You could golf the condition ? 0 : 1, but I wouldn't recommend it.

Answer 5

Although not strictly necessary, I would just use the Array's find function:

const getFirstCategory = (bonusPlus, prizeCategories) => {
  const bonusPlusLevel = bonusPlus ? 2 : 1;
  return prizeCategories.find( (cat) => {
    return cat.playLevel == bonusPlusLevel;
  });
};

(Borrowed partially from @kyrill)