TypeScript Best Practices for 2025

2 min read
TypeScript Best Practices for 2025

Why TypeScript?

TypeScript has become the de facto standard for building scalable JavaScript applications. Here's why it matters:

  • Type Safety: Catch errors before runtime
  • Better IDE Support: Autocomplete and refactoring
  • Self-Documenting Code: Types serve as documentation
  • Easier Refactoring: Confidence when making changes

Essential Patterns

1. Use unknown Instead of any

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

// ✅ Good
function processData(data: unknown) {
  if (typeof data === 'object' && data !== null && 'value' in data) {
    return (data as { value: string }).value
  }
  throw new Error('Invalid data')
}

2. Leverage Type Inference

TypeScript
// TypeScript can infer the return type
function add(a: number, b: number) {
  return a + b // inferred as number
}

3. Use Discriminated Unions

TypeScript
type Result<T> =
  | { success: true; data: T }
  | { success: false; error: string }

function handleResult<T>(result: Result<T>) {
  if (result.success) {
    console.log(result.data)
  } else {
    console.error(result.error)
  }
}

Advanced Tips

Const Assertions

TypeScript
const config = {
  apiUrl: 'https://api.example.com',
  timeout: 5000,
} as const

// config.apiUrl is now type 'https://api.example.com', not string

Generic Constraints

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

Conclusion

TypeScript is a powerful tool that, when used correctly, can significantly improve your development experience and code quality. Start with these patterns and build from there!