TypeScript Best Practices for 2026

TypeScript continues to evolve, and with it, our best practices. Here’s a comprehensive guide to writing better TypeScript code in 2026.

1. Enable Strict Mode

Always start with strict mode enabled in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "exactOptionalPropertyTypes": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true
  }
}

2. Use Type Inference Wisely

TypeScript’s inference is powerful. Don’t over-annotate:

// ✅ Good - Let TS infer
const user = { name: 'John', age: 30 };

// ❌ Unnecessary annotation
const user: { name: string; age: number } = { name: 'John', age: 30 };

3. Prefer Interfaces for Object Shapes

interface User {
  id: string;
  name: string;
  email: string;
  createdAt: Date;
}

function createUser(data: Omit<User, 'id' | 'createdAt'>): User {
  return {
    ...data,
    id: crypto.randomUUID(),
    createdAt: new Date(),
  };
}

4. Use Utility Types

Leverage built-in utility types for common transformations:

type PartialUser = Partial<User>;
type RequiredUser = Required<User>;
type ReadOnlyUser = Readonly<User>;
type UserNames = Pick<User, 'name'>;
type UserWithoutId = Omit<User, 'id'>;

5. Narrow Types with Type Guards

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

function processInput(input: string | number) {
  if (isString(input)) {
    // input is narrowed to string
    return input.toUpperCase();
  }
  return input.toFixed(2);
}

6. Avoid any - Use unknown Instead

// ❌ Avoid
function parseJSON(json: string): any {
  return JSON.parse(json);
}

// ✅ Better
function parseJSON<T = unknown>(json: string): T {
  return JSON.parse(json) as T;
}

7. Use Template Literal Types

type HttpMethod = 'GET' | 'POST' | 'PUT' | 'DELETE';
type Endpoint = '/users' | '/posts' | '/comments';

type ApiRoute = `${HttpMethod} ${Endpoint}`;
// Results in: "GET /users" | "POST /users" | ...

8. Implement Discriminated Unions

type Result<T, E = Error> =
  | { success: true; data: T }
  | { success: false; error: E };

function handleResult(result: Result<string>) {
  if (result.success) {
    console.log(result.data); // Type is string
  } else {
    console.error(result.error); // Type is Error
  }
}

9. Use Const Assertions

const colors = ['red', 'green', 'blue'] as const;
type Color = typeof colors[number]; // 'red' | 'green' | 'blue'

10. Create Reusable Type Utilities

type Nullable<T> = T | null;
type AsyncFunction<T, A extends unknown[]> = (...args: A) => Promise<T>;
type DeepPartial<T> = {
  [P in keyof T]?: T[P] extends object ? DeepPartial<T[P]> : T[P];
};

Conclusion

Following these best practices will help you write more maintainable, type-safe TypeScript code. Remember, the goal is not just to add types, but to make your code more self-documenting and less error-prone.

Happy coding! 🚀