Top 10 TypeScript Best Practices for Clean Code

TypeScript has become the go-to choice for developers who want to write more maintainable and scalable JavaScript applications. While TypeScript itself brings many advantages to the table, following best practices can take your code quality to the next level. Let’s dive into the top 10 TypeScript best practices that will help you write cleaner, more maintainable code.

1. Use Strict Type Checking

One of TypeScript’s greatest strengths is its type system. Enable strict type checking in your tsconfig.json to catch potential issues early:

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

This single setting helps prevent null references, ensures complete function implementations, and catches type-related bugs before they reach production.

2. Leverage Interface Over Type When Possible

While both interfaces and types can define object shapes, interfaces are often the better choice for object definitions. They’re more extensible and provide clearer error messages:

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

// Instead of
type User = {
  id: number;
  name: string;
  email: string;
}

3. Use Enums for Constants

When dealing with a fixed set of options, enums provide type safety and self-documentation:

enum UserRole {
  ADMIN = 'ADMIN',
  EDITOR = 'EDITOR',
  VIEWER = 'VIEWER'
}

4. Implement Proper Error Handling

Create custom error types for better error handling and debugging:

class ValidationError extends Error {
  constructor(message: string) {
    super(message);
    this.name = 'ValidationError';
  }
}

5. Use Type Guards for Runtime Checks

Type guards help narrow down types in a type-safe way:

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

6. Avoid Any Type

The any type defeats the purpose of using TypeScript. Instead, use unknown for values of uncertain types, then narrow them down:

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

// Good
function processData(data: unknown) {
  if (isValidData(data)) {
    // ...
  }
}

7. Utilize Generics for Reusable Code

Generics make your code more flexible while maintaining type safety:

function getLast\<T\>(array: T[]): T | undefined {
  return array[array.length - 1];
}

8. Implement Proper Null Checks

Use optional chaining and nullish coalescing operators for cleaner null checks:

const userName = user?.profile?.name ?? 'Anonymous';

9. Keep Types DRY (Don’t Repeat Yourself)

Extract common types to avoid repetition and maintain consistency:

interface HasId {
  id: number;
}

interface User extends HasId {
  name: string;
}

interface Product extends HasId {
  title: string;
}

10. Use Readonly for Immutable Data

Prevent accidental mutations by marking properties as readonly:

interface Config {
  readonly apiKey: string;
  readonly baseUrl: string;
}

Remember, these practices are guidelines rather than strict rules. The key is to maintain consistency throughout your project and adapt these practices to your specific needs. Happy coding!