typescript-best-practices

TypeScript Best Practices

Priority: P1 (OPERATIONAL)

Implementation Guidelines

• Naming: Classes/Types=PascalCase, vars/funcs=camelCase, consts=UPPER_SNAKE. Prefix I only if needed.
• Functions: Arrows for callbacks; regular for exports. Always type public API returns.
• Modules: Named exports only. Import order: external → internal → relative.
• Async: Use async/await, not raw Promises. Promise.all() for parallel.
• Classes: Explicit access modifiers. Favor composition. Use readonly.
• Types: Use never for exhaustiveness, asserts for runtime checks.
• Optional: Use ?:, not | undefined.
• Imports: Use import type for tree-shaking.

Anti-Patterns

• No Default Exports: Use named exports.
• No Implicit Returns: Specify return types.
• No Unused Variables: Enable noUnusedLocals.
• No require: Use ES6 import.
• No Empty Interfaces: Use type or non-empty interface.
• No any: NEVER use any. Force strict typing or use unknown with explicit casting.
• Mocking Strategy: In tests, use jest.Mocked<T> and cast values using value as unknown as T to satisfy strict linting without compromising type safety.
• NO LINT DISABLE: You are strictly PROHIBITED from using eslint-disable or ts-ignore comments. Fix underlying issues.

Reference & Examples

See references/examples.md for code samples including:

• Immutable Interfaces
• Exhaustiveness Checking
• Assertion Functions
• Dependency Injection Patterns
• Import Organization

Related Topics

language | tooling | security