After twelve years writing JavaScript across browsers, Node.js, and various runtime environments, I adopted TypeScript three years ago. The decision came from practical experience rather than industry trends. Too many production bugs originated from type mismatches that static analysis could have prevented during development.

Enable Strict Mode From the Start

TypeScript’s strict: true flag should be enabled from the beginning of any serious project. The configuration catches entire categories of errors that would otherwise surface in production:

// tsconfig.json
{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true
  }
}

Strict mode enforces null checking, prevents implicit any types, and validates function parameter usage. These constraints feel restrictive initially, but they surface problems with code structure that need addressing regardless.

Leverage Built-in Utility Types

TypeScript provides utility types that eliminate repetitive type definitions. The ones I use most frequently:

interface User {
  id: string;
  email: string;
  name: string;
  role: 'admin' | 'user';
}

// Update operations need optional fields
type UserUpdate = Partial<User>;

// Public API should omit sensitive fields
type PublicUser = Omit<User, 'email'>;

// Function return types can be extracted
function fetchUsers(): User[] { /* ... */ }
type FetchUsersReturn = ReturnType<typeof fetchUsers>;

These utilities compose well and prevent interface duplication across codebases.

Common Patterns to Avoid

Type assertions using as often indicate incorrect type modeling. When the type system requires frequent assertions, the underlying types need revision:

// Indicates the types are wrong
const user = data as User;

// Better: validate and narrow the type
function isUser(data: unknown): data is User {
  return typeof data === 'object' &&
         data !== null &&
         'id' in data &&
         'email' in data;
}

if (isUser(data)) {
  // TypeScript knows data is User here
  console.log(data.email);
}

TypeScript’s type inference is strong. Function parameters should have explicit types, but return types and local variables can often be inferred. Explicit annotations are needed at API boundaries and when inference produces overly broad types.

The Satisfies Operator

TypeScript 4.9 introduced the satisfies operator, which validates that a value matches a type without widening the inferred type:

type Color = 'red' | 'green' | 'blue';

// Inferred as specific strings, but validated against Color
const colors = {
  primary: 'red',
  secondary: 'blue'
} satisfies Record<string, Color>;

// colors.primary is type 'red', not Color

This preserves precise types while ensuring type safety, which is valuable for configuration objects and constant definitions.

When TypeScript Adds Value

TypeScript cannot fix architectural problems or eliminate logic errors. Its value lies in catching type mismatches, null reference errors, and refactoring mistakes before they reach production. The type system serves as executable documentation that stays synchronized with the code.

For long-lived codebases with multiple contributors, TypeScript reduces the cognitive overhead of understanding function contracts and data structures. For small scripts or rapid prototypes, the overhead may exceed the benefit.

The key is recognizing TypeScript as a tool with specific strengths. Use it where those strengths align with project needs. Configure strict mode to get the full benefit of static analysis. Write type guards and validation for external data. Let inference work where it produces correct types.

TypeScript has improved the reliability and maintainability of every production codebase where I have applied it properly.