Use Booleans Like a Pro

6 Essential Tips to Write Clean Booleans

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Motivation

Booleans are one of the simplest constructs in programming, yet it can often make code more complex and less straightforward. Booleans have only two possible values (true or false), yet I often see them poorly named and misused in many codebases.

In today’s article, I’ve gathered 4 naming and 2 usage tips relating to booleans. By applying these principles, you can avoid common pitfalls and Craft Better Software.

1️⃣ Avoid Negative Names

Negative boolean variables lead to double negatives, making your code harder to read and understand.

❌ if (!isNotActive)

✅ if (isActive)

The same happens in natural language: you use only one negative, because a double negative is just an affirmative sentence. Why would it be different with code?

You should write code that reads like natural language.

2️⃣ Use Adjectives

Don't use verbs or nouns in your boolean variable names. Booleans represent states, so they should be named with adjectives or short descriptive phrases instead.

❌ if (sendEvent)

✅ if (eventIsSent)

3️⃣ Use Present Tense

Boolean variables should describe the current state rather than past states. Using past or perfect tenses adds noise, making boolean variables wordy and less concise.

❌ if (hasBeenPaid)

✅ if (isPaid)

4️⃣ Use Is/Has/Should/Can Prefixes

One of my favorite tricks when naming booleans is to use prefixes. Consider using the following:

• is – for states (e.g., isActive)

• has – for ownership (e.g., hasSubscription)

• should – for expected behavior (e.g., shouldRetry)

• can – for capabilities (e.g., canEdit)

5️⃣ Avoid Boolean As Parameters

Using boolean flags in function parameters can be confusing and difficult to review. Instead, use enums to make your code self-documenting.

❌ Bad Examples:

bookFlight(customer, true);
bookFlight(customer, false);

✅ Good Examples:

bookFlight(customer, Discount.Applied);
bookFlight(customer, Discount.NotApplied);

Enums also help make your code open for changes. By extending the enum type with a new value, you can easily add new functionality without breaking the API.

6️⃣ Reduce Nesting With a Return Early

Using many IF-ELSE statements with booleans can easily lead to unreadable code. Avoid using nested IF statements.

Instead, invert the conditions and use guard clauses. It will make your code easier to follow. As a bonus, you will get rid of the ELSE statements:

Conclusion

Booleans are one of the most frequently used variable types. And if they are used right, they can greatly improve code quality.

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