Typescript Strict Mode

TypeScript Strict Mode Best Practices

Overview

This skill covers strict TypeScript practices applicable across all frameworks. It focuses on avoiding any, using proper type annotations, and leveraging TypeScript's type system for safer, more maintainable code.

The Golden Rule: NEVER Use any

CRITICAL RULE: Many codebases have @typescript-eslint/no-explicit-any enabled. Using any will cause build failures.

Why any is dangerous:

• Defeats the purpose of TypeScript's type system
• Hides bugs that would be caught at compile time
• Propagates type unsafety through the codebase
• Makes refactoring difficult and error-prone

Alternatives to any

1. Use Specific Types

❌ WRONG:

function processData(data: any) { ... }
const items: any[] = [];

✅ CORRECT:

function processData(data: { id: string; name: string }) { ... }
const items: string[] = [];

2. Use unknown When Type is Truly Unknown

unknown is the type-safe counterpart to any. It forces you to narrow the type before using it.

❌ WRONG: