TypeScript Best Practices in 2024

TypeScript has become the de facto standard for building large-scale JavaScript applications. Here are the best practices you should follow in 2024.

1. Use Strict Mode

Always enable strict mode in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true
  }
}

This enables all strict type checking options, helping catch bugs early.

2. Prefer Interfaces Over Type Aliases

For object types, prefer interfaces:

// Good
interface User {
  id: number
  name: string
  email: string
}

// Less preferred for objects
type User = {
  id: number
  name: string
  email: string
}

Interfaces are more extendable and have better error messages.

3. Use Union Types for Variants

Union types are perfect for representing different states:

type LoadingState = 
  | { status: 'idle' }
  | { status: 'loading' }
  | { status: 'success'; data: Data }
  | { status: 'error'; error: Error }

4. Avoid any Type

The any type defeats the purpose of TypeScript. Use proper types or unknown:

// Bad
function processData(data: any) {
  return data.value
}

// Good
function processData(data: unknown) {
  if (typeof data === 'object' && data !== null && 'value' in data) {
    return data.value
  }
}

5. Use Utility Types

TypeScript provides useful utility types:

// Partial - makes all properties optional
type PartialUser = Partial<User>

// Pick - select specific properties
type UserPreview = Pick<User, 'id' | 'name'>

// Omit - exclude properties
type UserWithoutEmail = Omit<User, 'email'>

6. Type Function Parameters and Returns

Always type your function parameters and return values:

function calculateTotal(items: Item[]): number {
  return items.reduce((sum, item) => sum + item.price, 0)
}

7. Use Enums for Constants

Enums are great for representing a fixed set of values:

enum UserRole {
  Admin = 'ADMIN',
  User = 'USER',
  Guest = 'GUEST'
}

Conclusion

Following these TypeScript best practices will help you write better, more maintainable code. TypeScript's type system is powerful—use it to your advantage!

Remember: Type safety is not a burden; it's a feature that saves time and prevents bugs. 🛡️