TypeScript Best Practices for Scalable Applications

TypeScript has become the standard for building robust web applications. After years of working with TypeScript, I've learned that following certain patterns can make a massive difference in code quality and developer experience.

Start Strict from Day One

The biggest mistake I see is not enabling strict mode from the start. Add these to your tsconfig.json:

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

These settings catch bugs before they reach production. Yes, they make TypeScript stricter, but that's the point.

Prefer Type Inference

Don't annotate everything. TypeScript is smart enough to infer most types:

// Bad
const name: string = "Nikolas";
const age: number = 25;

// Good
const name = "Nikolas";
const age = 25;

Explicit types are useful for function parameters and return types, but let TypeScript do the work elsewhere.

Use Discriminated Unions

Instead of optional properties, use discriminated unions for better type safety:

// Bad
type Response = {
  data?: User;
  error?: string;
};

// Good
type Response =
  | { success: true; data: User }
  | { success: false; error: string };

This pattern eliminates entire classes of runtime errors.

Avoid `any` Like the Plague

Every any you add is a hole in your type system. Use unknown instead when you truly don't know the type, and narrow it down with type guards.

Key Takeaways

Enable strict mode from the start
Let TypeScript infer types where possible
Use discriminated unions for complex states
Never use any without a very good reason

TypeScript's power comes from its type system. Embrace it, don't fight it.

Start Strict from Day One

Prefer Type Inference

Use Discriminated Unions

Avoid any Like the Plague

Key Takeaways

Avoid `any` Like the Plague