TypeScript Best Practices

TypeScript has become the standard for building robust JavaScript applications. Here are the best practices that will make you a TypeScript expert.

Use Strict Mode

Always enable strict mode in your tsconfig.json:

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

Type Inference

Let TypeScript infer types when possible:

// Good - let TypeScript infer
const name = 'John';
const age = 30;

// Unnecessary
const name: string = 'John';

Interface vs Type

Use interfaces for object shapes and types for unions:

// Interface for objects
interface User {
  name: string;
  email: string;
}

// Type for unions
type Status = 'pending' | 'approved' | 'rejected';

Generic Constraints

Use generic constraints for flexible, type-safe functions:

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

Utility Types

Leverage built-in utility types:

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

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

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

Const Assertions

Use const assertions for literal types:

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

Type Guards

Create custom type guards for runtime checks:

function isString(value: unknown): value is string {
  return typeof value === 'string';
}

Conclusion

Following these TypeScript best practices will help you write safer, more maintainable code. TypeScript’s type system is powerful when used correctly.