Push Null Values to the Perimeter of Your Types

Overview

Design types so values are either completely null or completely non-null, not a mix.

Mixed null states create implicit relationships that are hard to track and lead to scattered null checks and bugs.

When to Use This Skill

• Designing types with multiple nullable fields
• Finding null checks scattered throughout code
• Related values that are null together
• Debugging "undefined is not an object" errors
• Refactoring types with many optional properties

The Iron Rule