TypeScript Best Practices for Production Applications

Strict Mode Is Non-Negotiable

Always enable strict: true in your tsconfig. It catches entire categories of bugs at compile time. The small upfront cost pays off enormously in reduced runtime errors and better IDE support.

Prefer Interfaces Over Types (Usually)

Interfaces are extendable and produce better error messages. Use type aliases for unions, intersections, and mapped types where interfaces can't help.

Discriminated Unions

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

function handle(result: Result<User>) {
  if (result.success) {
    // TypeScript knows result.data exists here
    console.log(result.data.name);
  }
}

Zod for Runtime Validation

TypeScript only checks at compile time. Use Zod to validate data at runtime boundaries — API responses, form inputs, environment variables. The combination of TypeScript + Zod gives you end-to-end type safety.

Utility Types You Should Know

Partial<T> — make all properties optional
Pick<T, K> — select specific properties
Omit<T, K> — exclude specific properties
Record<K, V> — construct an object type with specific keys and values

TypeScript Best Practices for Production Apps