React Cookbook
“How would you do X?” — practical, production-ready recipes with the approach, full code, pitfalls and variations.
React
- Add optimistic updates to a todo listMake toggling and deleting items feel instant while staying correct if the server request fails.
- Build an accessible modal dialogShow a confirmation dialog that traps focus, closes with Escape and restores focus afterwards.
- Build infinite scroll with TanStack QueryLoad more items automatically as the user scrolls a long feed, using cursor pagination.
- Call a cookie-authenticated API with CSRF protectionYour SPA uses session cookies; send the CSRF token required by the backend on every mutating request.
- Debounce a search input in ReactSearch an API as the user types without firing a request on every keystroke or showing stale results.
- Handle errors gracefully with error boundariesShow a friendly fallback with a retry button when part of the UI crashes or fails to load data.
- Implement dark mode that follows the systemSupport light/dark themes with a manual override, persisted, and without a flash of the wrong theme.
- Poll a long-running job's statusShow progress for a report generation job until it finishes, then stop polling.
- Protect routes in a React SPAShow some pages only to signed-in users (and some only to admins), redirecting others to login and back.
- Refresh expired access tokens automaticallyRetry API calls transparently when the access token expires, without firing multiple refresh requests at once.
- Render 10,000 rows smoothly with virtualizationDisplay a very long list or table without freezing the browser.
- Respond to media queries in ReactRender different components for mobile and desktop and react to changes like dark mode or reduced motion.
- Show live updates over WebSocketsUpdate a dashboard in real time when the server pushes events, with reconnects.
- Show toast notifications from anywhereDisplay success and error messages from any component or mutation without prop drilling.
- Split your bundle by routeReduce initial JavaScript so the first page loads faster.
- Sync filters and pagination with the URLMake a filtered product list shareable and keep filters when the user refreshes or goes back.
- Test a data-fetching component with MSWWrite reliable tests for a component that loads data, including loading and error states.
- Upload files with a progress bar in ReactUpload large files directly to storage with a progress indicator and cancel button.
- Validate forms with React Hook Form and ZodBuild a signup form with field-level errors, server error mapping and accessible messages.
- Warn users about unsaved changesPrevent users from losing a half-filled form when navigating away or closing the tab.