TypeScript Best Practices for 2026

TypeScript has become the de facto standard for building JavaScript applications. Let's explore the best practices that will make your TypeScript code more maintainable and robust.

Use Strict Mode

Always enable strict mode in your tsconfig.json:

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

This catches many potential bugs at compile time.

Type Inference

Let TypeScript infer types when possible:

// Good - type is inferred
const users = [
  { name: "Alice", age: 30 },
  { name: "Bob", age: 25 },
];

// Unnecessary - type annotation not needed
const users: Array<{ name: string; age: number }> = [
  { name: "Alice", age: 30 },
  { name: "Bob", age: 25 },
];

Avoid any

The any type defeats the purpose of TypeScript:

// Bad
function process(data: any) {
  return data.value;
}

// Good
function process(data: { value: string }) {
  return data.value;
}

// Better - use generics
function process<T extends { value: string }>(data: T) {
  return data.value;
}

Use Type Guards

Create type-safe narrowing with type guards:

interface User {
  type: "user";
  name: string;
}

interface Admin {
  type: "admin";
  name: string;
  permissions: string[];
}

function isAdmin(user: User | Admin): user is Admin {
  return user.type === "admin";
}

function greet(user: User | Admin) {
  if (isAdmin(user)) {
    // TypeScript knows user is Admin here
    console.log(user.permissions);
  }
}

Leverage Utility Types

TypeScript provides powerful utility types:

interface User {
  id: string;
  name: string;
  email: string;
  password: string;
}

// Only id and name
type UserPreview = Pick<User, "id" | "name">;

// Everything except password
type PublicUser = Omit<User, "password">;

// All fields optional
type PartialUser = Partial<User>;

// All fields readonly
type ImmutableUser = Readonly<User>;

Discriminated Unions

Use discriminated unions for type-safe state management:

type LoadingState =
  | { status: "loading" }
  | { status: "success"; data: string }
  | { status: "error"; error: Error };

function handleState(state: LoadingState) {
  switch (state.status) {
    case "loading":
      return "Loading...";
    case "success":
      return state.data; // TypeScript knows data exists
    case "error":
      return state.error.message; // TypeScript knows error exists
  }
}

Const Assertions

Use as const for literal types:

// Type: string[]
const colors = ["red", "green", "blue"];

// Type: readonly ["red", "green", "blue"]
const colors = ["red", "green", "blue"] as const;

// Perfect for configuration objects
const config = {
  apiUrl: "https://api.example.com",
  timeout: 5000,
} as const;

Generic Constraints

Add constraints to generics for better type safety:

// Bad - too generic
function getValue<T>(obj: T, key: string) {
  return obj[key]; // Error: T doesn't have index signature
}

// Good - constrained generic
function getValue<T extends Record<string, any>, K extends keyof T>(
  obj: T,
  key: K
): T[K] {
  return obj[key]; // Type-safe!
}

const user = { name: "Alice", age: 30 };
const name = getValue(user, "name"); // Type: string
const age = getValue(user, "age"); // Type: number

Conclusion

These practices will help you write more maintainable TypeScript code. Remember:

• Enable strict mode
• Let TypeScript infer types when possible
• Avoid any like the plague
• Use type guards and utility types
• Leverage discriminated unions

Happy typing! 🎉