Top 10 TypeScript Best Practices Every Developer Should Follow

TypeScript, a superset of JavaScript, offers static typing, better tooling support, and improved maintainability. By following best practices, developers can write scalable and error-free applications.

In this article, we will explore the top 10 TypeScript best practices that will help you improve your code quality and maintainability.

1. Use Type Annotations Effectively

Type annotations improve readability and maintainability and prevent runtime errors.

✅ Good Practice (Using Type Annotations)

function greet(name: string): string {
  return `Hello, ${name}!`;
}

let age: number = 30;

❌ Bad Practice (No Type Annotations)

function greet(name) {
  return `Hello, ${name}!`;
}

let age = "30"; // Unexpected type usage

🔹 Why?

• Prevents unexpected type errors.
• Enhances code documentation.

📌 Tip: Always define types explicitly for function parameters, return values, and variables.

2. Use any Type Sparingly

Using any disables TypeScript's type-checking benefits, leading to potential errors.

✅ Good Practice (Using Specific Types)

function getUser(id: number): { id: number; name: string } {
  return { id, name: "John Doe" };
}

❌ Bad Practice (Using any)

function getUser(id: any): any {
  return { id, name: "John Doe" };
}

🔹 Why?

• Avoids losing type safety.
• Improves code predictability.

📌 Tip: Use specific types instead of any, or use unknown when necessary.

3. Use Interfaces for Objects

Interfaces ensure consistent object structures and improve code reusability.

✅ Good Practice (Using Interfaces)

interface User {
  id: number;
  name: string;
}

const user: User = { id: 1, name: "Alice" };

❌ Bad Practice (Using Loose Objects)

const user = { id: 1, name: "Alice" }; // No enforced structure

🔹 Why?

• Improves code maintainability.
• Enforces object structure.

📌 Tip: Use interfaces or type aliases for object definitions.

4. Prefer type for Union and Intersection Types

Use type for combining multiple types into a single entity.

✅ Good Practice (Using type)

type SuccessResponse = { success: true; data: string };
type ErrorResponse = { success: false; error: string };
type APIResponse = SuccessResponse | ErrorResponse;

❌ Bad Practice (Using Loose Objects)

const response = { success: true, data: "OK" };

🔹 Why?

• Ensures consistent API responses.
• Allows better type inference.

📌 Tip: Use type for union and intersection types.

5. Use Enums for Constants

Enums improve code readability by defining a set of named values.

✅ Good Practice (Using Enums)

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

let role: UserRole = UserRole.Admin;

❌ Bad Practice (Using String Constants)

const role = "ADMIN";

🔹 Why?

• Prevents invalid values.
• Improves code maintainability.

📌 Tip: Use Enums to define constant values.

6. Use readonly for Immutable Properties

Mark properties as readonly to prevent accidental modifications.

✅ Good Practice (Using readonly)

class User {
  readonly id: number;
  constructor(id: number) {
    this.id = id;
  }
}

❌ Bad Practice (Allowing Mutability)

class User {
  id: number;
  constructor(id: number) {
    this.id = id;
  }
}

🔹 Why?

• Prevents unintentional property modifications.
• Improves data integrity.

📌 Tip: Use readonly for properties that should not change.

7. Prefer unknown Over any

unknown is safer than any because it forces type checks before usage.

✅ Good Practice (Using unknown)

function processValue(value: unknown) {
  if (typeof value === "string") {
    console.log(value.toUpperCase());
  }
}

❌ Bad Practice (Using any)

function processValue(value: any) {
  console.log(value.toUpperCase()); // Runtime error if value is not a string
}

🔹 Why?

• Prevents unsafe operations.
• Ensures proper type checks.

📌 Tip: Use unknown instead of any when type is uncertain.

8. Use Optional Chaining and Nullish Coalescing

These features simplify handling null and undefined values.

✅ Good Practice (Optional Chaining & Nullish Coalescing)

const user = { profile: { name: "Alice" } };
console.log(user?.profile?.name ?? "Guest");

❌ Bad Practice (Manual Checks)

if (user && user.profile) {
  console.log(user.profile.name);
} else {
  console.log("Guest");
}

🔹 Why?

• Reduces boilerplate code.
• Prevents undefined errors.

📌 Tip: Use optional chaining (?.) and nullish coalescing (??).

9. Avoid Function Overloads with Conditional Types

Instead of multiple function overloads, use conditional types.

✅ Good Practice (Using Conditional Types)

function getLength<T extends string | any[]>(input: T): number {
  return input.length;
}

❌ Bad Practice (Multiple Overloads)

function getLength(input: string): number;
function getLength(input: any[]): number;
function getLength(input: any): number {
  return input.length;
}

🔹 Why?

• Reduces code duplication.
• Improves type inference.

📌 Tip: Use generic functions with conditional types.

10. Enable Strict Mode

Strict mode enforces better type safety.

✅ Good Practice (Enable strict Mode)

Set strict mode in tsconfig.json:

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

❌ Bad Practice (Loose Type Checking)

{
  "compilerOptions": {
    "strict": false
  }
}

🔹 Why?

• Prevents common errors.
• Improves code robustness.

📌 Tip: Always enable strict mode for better type safety.

Final Thoughts

Following these TypeScript best practices will help you write cleaner, safer, and more maintainable code. Whether you are a beginner or an experienced developer, applying these tips will enhance your TypeScript skills.

📢 What best practice do you follow? Share your thoughts in the comments! 🚀