React — Components, State and Effects for React 19

Overview

React 19.3 (September 2026) is the current release. React 19.0 added Actions, use and ref as a prop and removed long-deprecated APIs; 19.2 added useEffectEvent and <Activity>; 19.3 made <ViewTransition> and Fragment refs stable. React Compiler 1.0 memoises components at build time. This skill covers project setup, the APIs to write today, the effect and state mistakes that cause most bugs, the server/client boundary, and testing.

Instructions

Start a project

npm create vite@latest booking-desk -- --template react-compiler-ts --eslint   # client-rendered app
npx create-next-app@latest          # Server Components and server rendering
npx create-react-router@latest      # React Router framework mode

Create React App has been deprecated since February 2025; do not use it for new apps. The TypeScript templates for Vite are react-ts and react-compiler-ts. They lint with Oxlint unless --eslint is passed, which adds eslint-plugin-react-hooks with reactHooks.configs.flat.recommended.

Write React 19, not React 18