typescript

name	typescript
description	TypeScript development guidelines - strict config, functional programming, best practices
metadata	{"language":"typescript","audience":"developers"}

Configuration

When working in a TypeScript project:

1. Check for tsconfig.json - Always verify the project has a tsconfig.json
2. If missing: Install typescript as dev dependency, then run npx tsc --init
3. Use strictest options - Configure the strictest possible compilerOptions:
   • strict: true
   • noUncheckedIndexedAccess: true
   • noImplicitReturns: true
   • noFallthroughCasesInSwitch: true
   • exactOptionalPropertyTypes: true
   • noImplicitOverride: true

Reference: https://www.typescriptlang.org/tsconfig/

Functional Programming

Favor functional programming when coding in TypeScript:

• Immutability - Use const, spread operators, Object.freeze(), immutable data structures
• Pure functions - Same input always produces same output, no side effects
• No side-effects - Prefer pure functions, isolate side effects to specific layers
• No throw - Use Result/Either types for error handling instead of exceptions

Type Safety

• Prefer type over interface for unions and primitives
• Use unknown over any - always narrow types before use
• Enable strictNullChecks - handle null/undefined explicitly
• Use utility types (Partial, Required, Readonly, Record, etc.)
• Avoid as assertions; prefer type guards