How to use Claude Code for JavaScript and TypeScript development. React, Next.js, Node.js, and modern JS/TS patterns with AI assistance.
Claude Code for JavaScript and TypeScript: Complete Guide
JavaScript and TypeScript dominate modern web development. React frontends, Node.js backends, Next.js full-stack apps.
Claude Code excels at all of it. Here's how to maximize it for JS/TS development.
Why JS/TS Developers Love Claude Code
- Framework fluency - Deep understanding of React, Next.js, Express, etc.
- Type safety - Generates properly typed TypeScript
- Modern patterns - Uses current best practices, not outdated patterns
- Full-stack understanding - Handles frontend and backend seamlessly
- Package ecosystem - Knows npm packages and their proper usage
Setup for JS/TS Projects
Basic Setup
cd your-project
claude
Claude Code detects JS/TS projects from:
package.jsontsconfig.json.js, .ts, .jsx, .tsx files
TypeScript Configuration
Claude Code reads your tsconfig.json and follows your settings:
- Strict mode
- Path aliases
- Module resolution
- Target version
Tell Claude Code about special configs:
> We use path aliases like @/components and @/lib.
Create a new utility following this pattern.
React Development
Creating Components
> Create a DataTable component with:
- Sortable columns
- Pagination
- Search filtering
- TypeScript types for props
- Loading and empty states
Claude Code generates:
interface Column<T> {
key: keyof T;
header: string;
sortable?: boolean;
render?: (value: T[keyof T], row: T) => React.ReactNode;
}
interface DataTableProps<T> {
data: T[];
columns: Column<T>[];
pageSize?: number;
isLoading?: boolean;
onRowClick?: (row: T) => void;
}
export function DataTable<T extends { id: string | number }>({
data,
columns,
pageSize = 10,
isLoading = false,
onRowClick
}: DataTableProps<T>) {
const [sortConfig, setSortConfig] = useState<{
key: keyof T;
direction: 'asc' | 'desc';
} | null>(null);
const [currentPage, setCurrentPage] = useState(1);
const [searchQuery, setSearchQuery] = useState('');
// ... implementation
}
React-Specific Prompts
> Convert the UserProfile class component to
a functional component with hooks.
> Add React Query for data fetching in the
dashboard page. Handle loading and error states.
> Create a custom useDebounce hook and use it
in the search input.
React Performance
> Optimize the ProductList component:
- Add proper memoization
- Virtualize the list for large datasets
- Lazy load images
- Split into smaller components
Next.js Development
App Router (Next.js 14+)
> Create a products page using App Router:
- Server component for data fetching
- Client component for interactivity
- Loading and error boundaries
- Dynamic metadata
- Proper TypeScript types
Claude Code generates modern Next.js:
// app/products/page.tsx
import { Suspense } from 'react';
import { ProductGrid } from './product-grid';
import { ProductSkeleton } from './product-skeleton';
export const metadata = {
title: 'Products | Your Store',
description: 'Browse our product catalog'
};
async function getProducts() {
const res = await fetch('https://api.example.com/products', {
next: { revalidate: 3600 }
});
return res.json();
}
export default async function ProductsPage() {
const products = await getProducts();
return (
<main className="container mx-auto py-8">
<h1 className="text-3xl font-bold mb-6">Products</h1>
<Suspense fallback={<ProductSkeleton />}>
<ProductGrid products={products} />
</Suspense>
</main>
);
}
Next.js-Specific Prompts
> Add a Server Action for the contact form
with validation using Zod.
> Create an API route for webhook handling
with signature verification.
> Set up middleware for authentication
checking on protected routes.
Node.js Backend
Express APIs
> Create an Express API for user management:
- TypeScript with strict mode
- JWT authentication middleware
- Request validation with Zod
- Error handling middleware
- Rate limiting
Node.js-Specific Prompts
> Add a background job processor using Bull
for sending emails asynchronously.
> Create a WebSocket handler for real-time
notifications using Socket.io.
> Add comprehensive logging with Pino,
including request tracing.
TypeScript Best Practices
Type Generation
> Generate TypeScript types from the OpenAPI
spec in api/openapi.yaml.
Generic Utilities
> Create a type-safe API client wrapper
with automatic error handling and retry logic.
Claude Code generates advanced TypeScript:
type ApiResponse<T> =
| { success: true; data: T }
| { success: false; error: ApiError };
interface ApiClientConfig {
baseUrl: string;
headers?: Record<string, string>;
retries?: number;
}
export function createApiClient(config: ApiClientConfig) {
const { baseUrl, headers = {}, retries = 3 } = config;
async function request<T>(
endpoint: string,
options?: RequestInit
): Promise<ApiResponse<T>> {
// Implementation with retry logic
}
return {
get: <T>(endpoint: string) => request<T>(endpoint),
post: <T, D>(endpoint: string, data: D) =>
request<T>(endpoint, {
method: 'POST',
body: JSON.stringify(data)
}),
// ... other methods
};
}
Zod Integration
> Add Zod validation to all API endpoints.
Generate types from schemas.
Testing JavaScript/TypeScript
Jest Tests
> Write Jest tests for the AuthService:
- Mock external dependencies
- Test success and error cases
- Use TypeScript for type safety
React Testing Library
> Add tests for the DataTable component:
- Rendering with different data
- Sorting interaction
- Pagination behavior
- Empty and loading states
E2E with Playwright
> Create Playwright tests for the checkout flow:
- Add item to cart
- Fill shipping form
- Complete payment
- Verify confirmation
Modern JavaScript Patterns
Using Modern Features
> Refactor using modern JavaScript:
- Optional chaining
- Nullish coalescing
- Array methods (map, filter, reduce)
- Destructuring
- Template literals
Async Patterns
> Convert callback-based code to async/await.
Add proper error handling.
Claude Code generates clean async code:
// Before
function fetchUserData(id, callback) {
fetch(`/api/users/${id}`)
.then(res => res.json())
.then(user => {
fetch(`/api/orders?userId=${user.id}`)
.then(res => res.json())
.then(orders => callback(null, { user, orders }))
.catch(err => callback(err));
})
.catch(err => callback(err));
}
// After (Claude Code refactored)
async function fetchUserData(id: string): Promise<UserWithOrders> {
const user = await fetchJson<User>(`/api/users/${id}`);
const orders = await fetchJson<Order[]>(`/api/orders?userId=${user.id}`);
return { user, orders };
}
Package Management
Adding Dependencies
> Add form validation with react-hook-form
and Zod. Create a reusable form component.
Updating Packages
> Update React from 17 to 18. Handle any
breaking changes in our components.
Removing Unused
> Find and remove unused dependencies
from package.json.
Build and Bundling
Optimization
> Optimize the webpack/Vite config for:
- Code splitting
- Tree shaking
- Asset optimization
- Bundle analysis
CI/CD
> Create GitHub Actions workflow for:
- Type checking
- Linting
- Testing
- Building
- Deploying to Vercel
Common JS/TS Tasks
| Task |
Prompt |
| New component |
"Create a Modal component with TypeScript" |
| API endpoint |
"Add POST /api/users endpoint with validation" |
| State management |
"Add Zustand store for cart state" |
| Form handling |
"Create login form with react-hook-form" |
| Data fetching |
"Add React Query for product data" |
| Styling |
"Add Tailwind styles to the Header component" |
| Animation |
"Add Framer Motion animations to the page transitions" |
Framework-Specific Tips
React
> We use React 18 with Suspense. Create components
that work with streaming SSR.
Next.js
> We're on Next.js 14 App Router. Use Server Components
by default, Client Components only when needed.
Express
> We use Express 5 with the promise router.
Create async route handlers.
The Bottom Line
Claude Code understands modern JavaScript and TypeScript deeply:
- Framework conventions (React, Next.js, Express)
- Type safety and generics
- Modern ES features
- Testing patterns
- Build tooling
Be specific about your project's stack, and Claude Code adapts to your patterns.
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