TypeScript Best Practices for 2025

TypeScript has become essential for modern web development. Here are the best practices I follow in 2025.

1. Use Strict Mode

Always enable strict mode in tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "noImplicitOverride": true
  }
}

2. Avoid 'any' Type

Use 'unknown' instead:

// Bad
function process(data: any) {}
// Good
function process(data: unknown) {
  if (typeof data === 'string') {
    // TypeScript knows data is string here
  }
}

3. Use Type Guards

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

4. Leverage Utility Types

type User = {
  id: string
  name: string
  email: string
  password: string
}
// Pick specific properties
type PublicUser = Pick
// Omit sensitive data
type SafeUser = Omit
// Make all properties optional
type PartialUser = Partial
// Make all properties required
type RequiredUser = Required

5. Use Generics Wisely

function getFirstElement(arr: T[]): T | undefined {
  return arr[0]
}
const num = getFirstElement([1, 2, 3]) // number | undefined
const str = getFirstElement(['a', 'b']) // string | undefined

6. Discriminated Unions

type Success = {
  status: 'success'
  data: User
}
type Error = {
  status: 'error'
  message: string
}
type Result = Success | Error
function handleResult(result: Result) {
  if (result.status === 'success') {
    // TypeScript knows result.data exists
    console.log(result.data)
  } else {
    // TypeScript knows result.message exists
    console.log(result.message)
  }
}

7. Const Assertions

const config = {
  apiUrl: 'https://api.example.com',
  timeout: 5000,
} as const
// config.apiUrl is 'https://api.example.com', not string
// config is readonly

8. Template Literal Types

type EventName = 'click' | 'focus' | 'blur'
type EventHandler = on${Capitalize}
// 'onClick' | 'onFocus' | 'onBlur'

9. Branded Types

type UserId = string & { __brand: 'UserId' }
type ProductId = string & { __brand: 'ProductId' }
function getUser(id: UserId) {}
const userId = 'user-123' as UserId
const productId = 'prod-456' as ProductId
getUser(userId) // OK
getUser(productId) // Error!

10. Use satisfies Operator

type Config = {
  apiUrl: string
  timeout: number
}
const config = {
  apiUrl: 'https://api.example.com',
  timeout: 5000,
  extra: 'allowed', // OK
} satisfies Config

Conclusion

TypeScript is powerful when used correctly. These practices will help you write safer, more maintainable code.

Need TypeScript expertise? I'm available for code reviews and consulting. [Contact me](/contact)