TypeScript Professional
Strict TypeScript patterns for professional development.
Instructions
1. Strict Mode Configuration
Always enable strict mode in tsconfig.json:
{
"compilerOptions": {
"strict": true,
"noImplicitAny": true,
"strictNullChecks": true,
"noUnusedLocals": true,
"noUnusedParameters": true
}
}2. Naming Conventions
| Type | Convention | Example |
|---|---|---|
| Interface | PascalCase, prefix with I (optional) | User, IUserService |
| Type | PascalCase | UserRole, ApiResponse |
| Enum | PascalCase | Status, Direction |
| Function | camelCase | getUserById, calculateTotal |
| Variable | camelCase | userName, isLoading |
| Constant | UPPER_SNAKE_CASE | MAX_RETRY_COUNT, API_URL |
3. Type vs Interface
// ✅ Interface for object shapes
interface User {
id: string;
name: string;
email: string;
}
// ✅ Type for unions, intersections, primitives
type Status = 'pending' | 'active' | 'inactive';
type ApiResponse<T> = { data: T; error: null } | { data: null; error: string };4. Never Use any
// ❌ Bad
function process(data: any) { ... }
// ✅ Good - use unknown and narrow
function process(data: unknown) {
if (typeof data === 'string') {
return data.toUpperCase();
}
}
// ✅ Good - use generics
function process<T>(data: T): T { ... }5. Utility Types
// Partial - all optional
type PartialUser = Partial<User>;
// Required - all required
type RequiredUser = Required<User>;
// Pick - select specific
type UserName = Pick<User, 'name'>;
// Omit - exclude specific
type UserWithoutId = Omit<User, 'id'>;
// Record - key-value mapping
type UserMap = Record<string, User>;6. Function Types
// ✅ Explicit return types for public APIs
function getUser(id: string): Promise<User | null> {
// ...
}
// ✅ Arrow function with types
const add = (a: number, b: number): number => a + b;7. Generics
// ✅ Constrained generics
function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
return obj[key];
}
// ✅ Default generic types
interface ApiResponse<T = unknown> {
data: T;
status: number;
}