Use an object instead of a switch

Sometimes we can do a simple refactor and achieve a lot with it! The example I’m gonna show was taken from a real project that has been working just fine for a long time. Still, that doesn’t mean we shouldn’t take the initiative to improve simply because it’s already working. However, we also need to be pragmatic and not fall into the perfectionism trap. Basically, we should find the sweet spot where the effort necessary is paid by its own results.

I was working on a module that had a getMonth function which would return the translation key according to the given month:

const getMonth = (month: string) => {
  let translationKey = "";
  switch (month) {
    case "January":
      translationKey = "JANUARY_TRANSLATION_KEY";
      break;
    case "February":
      translationKey = "FEBRUARY_TRANSLATION_KEY";
      break;
    case "March":
      translationKey = "MARCH_TRANSLATION_KEY";
      break;
    case "April":
      translationKey = "APRIL_TRANSLATION_KEY";
      break;
    case "May":
      translationKey = "MAY_TRANSLATION_KEY";
      break;
    case "June":
      translationKey = "JUNE_TRANSLATION_KEY";
      break;
    case "July":
      translationKey = "JULY_TRANSLATION_KEY";
      break;
    case "August":
      translationKey = "AUGUST_TRANSLATION_KEY";
      break;
    case "September":
      translationKey = "SEPTEMBER_TRANSLATION_KEY";
      break;
    case "October":
      translationKey = "OCTOBER_TRANSLATION_KEY";
      break;
    case "November":
      translationKey = "NOVEMBER_TRANSLATION_KEY";
      break;
    case "December":
      translationKey = "DECEMBER_TRANSLATION_KEY";
  }
  return translationKey;
};

In this case, it was clear to me what I would accomplish using an object instead of a switch statement: readability and reduce the cognitive complexity (you can read more about it here)

Why an object? Well, if you take a closer look at what the getMonth function is doing, you realize that it’s doing nothing but mapping keys to values, which is exactly what an object does!

Therefore, a switch statement isn’t needed at all. actually, it just makes the code less readable and increases its cognitive complexity. So, after refactoring:

const MONTH_TO_TRANSLATION_KEY = {
  January: "JANUARY_TRANSLATION_KEY",
  February: "FEBRUARY_TRANSLATION_KEY",
  March: "MARCH_TRANSLATION_KEY",
  April: "APRIL_TRANSLATION_KEY",
  May: "MAY_TRANSLATION_KEY",
  June: "JUNE_TRANSLATION_KEY",
  July: "JULY_TRANSLATION_KEY",
  August: "AUGUST_TRANSLATION_KEY",
  September: "SEPTEMBER_TRANSLATION_KEY",
  October: "OCTOBER_TRANSLATION_KEY",
  November: "NOVEMBER_TRANSLATION_KEY",
  December: "DECEMBER_TRANSLATION_KEY",
} as const;

type Month = keyof typeof MONTH_TO_TRANSLATION_KEY;

const getMonth = (month: Month) => MONTH_TO_TRANSLATION_KEY[month];

tl;dr: whenever we notice that the switch is doing nothing more than mapping keys to values, we could use an object instead.