Simpler conditionals with Guard Clauses

Nested conditionals can make your code harder to read and change—especially if you nest them more than one level.

Below, I'll show an example of a function that returns a discount for the provided user.

• It should give a 20% discount for all regular users.
• But if the user has a premium membership, it will give a 40% discount.
• Gold users take the highest discount: 60%.
• If the user is banned, however, it should not give any discount.

Without guard clauses, I'll write this function like this:

function getDiscountForUser(user) {
  let result
  if (user.isBanned) {
    result = 0
  } else {
    if (user.isPremium) {
      result = 40
    } else {
      if (user.isGold) {
        result = 60
      } else {
        result = 20
      }
    }
  }
  return result
}

I'll show you below how guard clauses can make it much simpler. But first, what are guard clauses?

#What are Guard Clauses?

Guard clauses are the checks you put at the beginning of a function to check for the unusual conditions.

A usual (or called normal) condition is the condition that represents most cases for the needed behavior—in this case it's regular users getting a 20% discount. Anything other than that is called an unusual condition.

Guard clauses also return immediately if true—preventing other conditions from running.

Here's how the same function looks but with guard clauses:

function getDiscountForUser(user) {
  if (user.isBanned) return 0
  if (user.isPremium) return 40
  if (user.isGold) return 60

  return 20
}

With the beauty of guard clauses, the function became way much easier to read and change.