TypeScript Best Practices for Production Applications

Why TypeScript Matters

TypeScript brings type safety, better tooling, and improved maintainability to JavaScript projects. These practices will help you build production-ready TypeScript applications.

Essential TypeScript Practices

1. Strict Mode

Enable strict mode in tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true
  }
}

This catches errors at compile time, not runtime.

2. Use Meaningful Type Names

Instead of generic names, use descriptive ones:

// Bad
type User = { name: string; email: string }

// Good
type CustomerAccount = {
  displayName: string
  emailAddress: string
}

3. Prefer Interfaces for Objects

Use interfaces for object shapes, types for unions/intersections:

interface User {
  id: string
  name: string
}

type Status = 'active' | 'inactive' | 'pending'

4. Avoid any

Use unknown instead of any when you need type flexibility:

function processData(data: unknown) {
  if (typeof data === 'string') {
    // TypeScript knows data is string here
    return data.toUpperCase()
  }
}

5. Use Utility Types

Leverage built-in utility types:

• Partial<T> - Makes all properties optional
• Pick<T, K> - Select specific properties
• Omit<T, K> - Exclude specific properties
• Record<K, V> - Create object types

6. Type Your Functions

Always type function parameters and return values:

function calculateTotal(
  items: CartItem[],
  taxRate: number
): number {
  // Implementation
}

7. Use Enums Sparingly

Prefer union types for simple constants:

// Better than enum
type Theme = 'light' | 'dark' | 'auto'

8. Generic Constraints

Use generic constraints to maintain type safety:

function getProperty<T, K extends keyof T>(
  obj: T,
  key: K
): T[K] {
  return obj[key]
}

Project Structure Best Practices

Separate Types

Create dedicated type files:

src/
  types/
    user.ts
    api.ts
    common.ts

Use Type Guards

Create functions that narrow types:

function isUser(obj: unknown): obj is User {
  return (
    typeof obj === 'object' &&
    obj !== null &&
    'id' in obj &&
    'name' in obj
  )
}

Common Pitfalls to Avoid

1. Overusing as assertions - Use type guards instead

2. Ignoring compiler errors - Fix them immediately

3. Complex type gymnastics - Keep types simple and readable

4. Mixing JavaScript and TypeScript - Gradually migrate fully

Testing with TypeScript

TypeScript catches many errors, but you still need tests:

• Unit tests for business logic
• Integration tests for workflows
• Type tests for complex types

Conclusion

TypeScript is a powerful tool when used correctly. Follow these practices to build maintainable, type-safe applications that scale.

Ready to improve your TypeScript codebase? Let's discuss how we can help.