Prefer More Precise Alternatives to Index Signatures

Overview

Index signatures are imprecise. Use interfaces, Records, or Maps instead.

Index signatures ({[key: string]: T}) allow any string key, don't require specific keys, and can't have different types for different keys. There are almost always better alternatives.

When to Use This Skill

• Defining types with known property names
• Modeling data from APIs or configuration files
• Working with CSV or dynamic data
• Choosing between object types and Maps

The Iron Rule