React

React

Editor's note: This guide was updated by Amazing Enyichi Agu in January 2026 to reflect React Router v7. The update refreshes the setup and examples (Vite + React + TypeScript), switches to the react-router package, introduces React Router's modes (declarative, data, framework), and revises the routing, nested routes, params, useRoutes, and route protection sections to match current v7 patterns. Single-page applications (SPAs) with multiple views need a mechanism for users to navigate between those different views without refreshing the whole webpage.

It's been another challenging week for the React ecosystem. Developers worldwide have been rushing to update their React versions to patch two new vulnerabilities. This serves as a good reminder for all of us to prioritize security during testing. Fortunately, React Native remains mostly unaffected by these threats, as Server Components aren't yet widely used in the mobile environment. We are taking a well-deserved Christmas break 🎄 so this will be our last issue until January 14th.

React, the widely adopted JavaScript library for building user interfaces, has reached a milestone with the stable release of React Compiler 1.0, built on top of nearly a decade of engineering work and compiler learnings that transforms how developers optimize React applications. React Compiler 1.0 is a build-time tool that optimizes React apps through automatic memoization, working on both React and React Native without requiring code rewrites.

When you are building a social feed, data grid, or chat UI, everything feels fine with 10 mock items. Then you connect a real API, render 50,000 rows with myList.map(...), and the browser locks up. The core problem is simple: you are asking the DOM to do too much work. Virtualization solves this by rendering only what the user can actually see. Instead of mounting 50,000 nodes, you render the 15-20 items that are visible in the viewport, plus a small buffer.

When CSS Grid layout was first released, it came with a big asterisk: only the grid's direct children could participate in the layout. "Subgrid" is a newer addition to CSS Grid which allows us to extend the grid layout down through the DOM tree. When I first heard about subgrid, it seemed to me like a convenience, a way to make it a bit simpler to accomplish the same stuff I was already doing.

Vercel's AI SDK solved the complex challenge of integrating AI into applications. AI SDK provides a unified TypeScript toolkit that abstracts away the complexity of working with various large language models (LLMs). However, as developers adopted AI SDK for backend integration, they faced a new challenge: crafting great frontend user interfaces for AI applications. Building conversational UIs, message displays, and interactive elements required significant time and expertise.