TypeScript Best Practices for 2025
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2 min read
TypeScriptJavaScriptBest Practices
Introduction
TypeScript has become the de facto standard for building large-scale JavaScript applications. This guide covers essential best practices for writing clean, type-safe TypeScript code.
Type Safety First
Use Strict Mode
Always enable strict mode in your tsconfig.json:
{
"compilerOptions": {
"strict": true,
"noUncheckedIndexedAccess": true,
"noImplicitOverride": true
}
}Avoid any Type
Instead of using any, use more specific types:
// Bad
function processData(data: any) {
return data.map((item: any) => item.value);
}
// Good
function processData<T extends { value: unknown }>(data: T[]) {
return data.map((item) => item.value);
}Advanced Type Patterns
Discriminated Unions
Use discriminated unions for type-safe state management:
type LoadingState = { status: 'loading' };
type SuccessState<T> = { status: 'success'; data: T };
type ErrorState = { status: 'error'; error: Error };
type AsyncState<T> = LoadingState | SuccessState<T> | ErrorState;
function handleState<T>(state: AsyncState<T>) {
switch (state.status) {
case 'loading':
return 'Loading...';
case 'success':
return state.data;
case 'error':
return state.error.message;
}
}Utility Types
Leverage TypeScript's built-in utility types:
interface User {
id: string;
name: string;
email: string;
password: string;
}
// Public user without password
type PublicUser = Omit<User, 'password'>;
// Partial update
type UserUpdate = Partial<User>;
// Read-only user
type ReadonlyUser = Readonly<User>;Function Overloading
Use function overloading for better type inference:
function createElement(tag: 'a'): HTMLAnchorElement;
function createElement(tag: 'div'): HTMLDivElement;
function createElement(tag: string): HTMLElement;
function createElement(tag: string): HTMLElement {
return document.createElement(tag);
}
const anchor = createElement('a'); // Type: HTMLAnchorElementConclusion
Following these TypeScript best practices will help you write more maintainable, type-safe code. Remember to leverage the type system to catch errors at compile time rather than runtime.
Happy coding!