operate saveUser(
  person: Person,
  emailOption: WelcomeEmailOption,
  verificationStatus: VerificationStatus
): void {
  if (emailOption === WelcomeEmailOption.Ship) {
    sendEmail(person.e-mail, 'Welcome!');
  }
  if (verificationStatus === VerificationStatus.Verified) {
    person.verified = true;
  }
  // save person to database...
}

And you may name it like this:

saveUser(newUser, WelcomeEmailOption.Ship, VerificationStatus.Unverified); 

Isn’t that loads simpler in your mind? That decision reads like documentation. It’s clear and to the purpose, and the maintainer can see instantly what the decision does and what the parameters imply. 

Booleans are a lure for future complexity

A bonus of enums is they’re expandable. Think about you will have a meals and beverage system that has small and huge sized drinks. You may find yourself with

var IsSmallDrink: boolean;

And also you construct your system round that Boolean variable, even having Boolean fields within the database for that info. However then the boss comes alongside and says, “Hey, we’re going to begin promoting medium drinks!”

Uh oh, that is going to be a significant change. Out of the blue, a easy Boolean has change into a legal responsibility. However when you had averted Booleans and began with

enum DrinkSize {
  Small,
  Massive
}

Then including one other drink measurement turns into a lot simpler.

Look, Booleans are highly effective and easy. I’m sufficiently old to recollect when languages didn’t even have Boolean varieties. We needed to simulate them with integers:

10 LET FLAG = 0
20 IF FLAG = 1 THEN PRINT "YOU WILL NEVER SEE THIS"
30 LET FLAG = 1
40 IF FLAG = 1 THEN PRINT "NOW IT PRINTS"
50 END

So I perceive their attraction. However utilizing Booleans finally ends up being fraught with peril. Are there exceptions? Certain, there are easy circumstances the place issues really are and all the time might be both true or false—like isLoading. However if you’re in a rush, otherwise you let your guard down, or perhaps you’re feeling a bit lazy, you possibly can simply fall into the lure of writing convoluted, hard-to-reason-about code. So tread flippantly and punctiliously earlier than utilizing a Boolean variable.