React SPA Development

Overview

Client-side React 19+ SPAs. Stack: React Router v7 (routing/loaders), Jotai (atomic global state), Vite (build), Bun (package manager/runtime). NOT for SSR frameworks (Next.js/Remix) — those are out of scope.

The single densest section is Expert Practices at the end — read it first if you know React basics. The middle sections are reference implementations.

React 19 Features

Actions and useActionState

React 19 introduces Actions for handling async state transitions:

import { useActionState } from 'react'