TypeScript Best Practices for 2025

TypeScript Best Practices

TypeScript has evolved significantly. Here are the best practices for writing modern TypeScript code in 2025.

1. Embrace Strict Mode

Always enable strict mode in your tsconfig.json:

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

2. Use Type Inference

Let TypeScript infer types when obvious:

// ❌ Overly explicit
const name: string = "John"
const numbers: number[] = [1, 2, 3]

// ✅ Let TypeScript infer
const name = "John"
const numbers = [1, 2, 3]

3. Prefer Interfaces Over Type Aliases

For object shapes, interfaces are more performant:

// ✅ Good
interface User {
  id: string
  name: string
  email: string
}

// Use type aliases for unions and intersections
type Status = "pending" | "active" | "inactive"

4. Leverage Utility Types

TypeScript provides powerful utility types:

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

// Create variations easily
type PublicUser = Omit<User, "password">
type PartialUser = Partial<User>
type ReadonlyUser = Readonly<User>

5. Avoid the any Type

Instead of any, use unknown for truly unknown types:

// ❌ Avoid
function processData(data: any) {
  // No type safety
}

// ✅ Better
function processData(data: unknown) {
  // Must validate before use
  if (typeof data === 'string') {
    console.log(data.toUpperCase())
  }
}

6. Use Const Assertions

For literal types and readonly objects:

// Literal type
const config = {
  api: "https://api.example.com",
  timeout: 5000
} as const

// Array of literals
const colors = ["red", "green", "blue"] as const
type Color = typeof colors[number] // "red" | "green" | "blue"

Conclusion

TypeScript is more than just "JavaScript with types". By following these practices, you'll write more maintainable, self-documenting code that catches errors before they reach production.