Introduction
TypeScript has become the standard for building scalable JavaScript applications. This guide covers essential best practices for writing clean, type-safe TypeScript code.
Type Safety First
Always leverage TypeScriptβs type system to catch errors at compile time:
// Good: Explicit types
interface User {
id: string
name: string
email: string
}
function getUser(id: string): User {
// Implementation
}
// Avoid: Using 'any'
function processData(data: any) {
// Type safety lost
}
Use Strict Mode
Enable strict mode in your tsconfig.json:
{
"compilerOptions": {
"strict": true,
"noImplicitAny": true,
"strictNullChecks": true
}
}
Utility Types
TypeScript provides powerful utility types:
// Partial - makes all properties optional
type PartialUser = Partial<User>
// Pick - select specific properties
type UserPreview = Pick<User, 'name' | 'email'>
// Omit - exclude specific properties
type UserWithoutId = Omit<User, 'id'>
Discriminated Unions
Use discriminated unions for type-safe state management:
type LoadingState =
| { status: 'idle' }
| { status: 'loading' }
| { status: 'success'; data: User[] }
| { status: 'error'; error: string }
function renderState(state: LoadingState) {
switch (state.status) {
case 'loading':
return 'Loading...'
case 'success':
return state.data.map(user => user.name)
case 'error':
return state.error
default:
return null
}
}
Generic Constraints
Use generic constraints to create flexible, type-safe functions:
function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
return obj[key]
}
const user: User = { id: '1', name: 'John', email: 'john@example.com' }
const name = getProperty(user, 'name') // Type: string
Conclusion
Following these TypeScript best practices will help you write more maintainable, error-free code. Start with strict mode, leverage the type system, and use advanced features like discriminated unions and generics.
