v19.2Latest

Introduction

React Compiler is a new build-time tool that automatically optimizes your React app. It works with plain JavaScript, and understands the Rules of React, so you don’t need to rewrite any code to use it.

You will learn
  • What React Compiler does
  • Getting started with the compiler
  • Incremental adoption strategies
  • Debugging and troubleshooting when things go wrong
  • Using the compiler on your React library

What does React Compiler do?

React Compiler automatically optimizes your React application at build time. React is often fast enough without optimization, but sometimes you need to manually memoize components and values to keep your app responsive. This manual memoization is tedious, easy to get wrong, and adds extra code to maintain. React Compiler does this optimization automatically for you, freeing you from this mental burden so you can focus on building features.

Before React Compiler

Without the compiler, you need to manually memoize components and values to optimize re-renders:

Note

This manual memoization has a subtle bug that breaks memoization:

Even though handleClick is wrapped in useCallback, the arrow function () => handleClick(item) creates a new function every time the component renders. This means that Item will always receive a new onClick prop, breaking memoization.

React Compiler is able to optimize this correctly with or without the arrow function, ensuring that Item only re-renders when props.onClick changes.

After React Compiler

With React Compiler, you write the same code without manual memoization:

See this example in the React Compiler Playground

React Compiler automatically applies the optimal memoization, ensuring your app only re-renders when necessary.

Deep Dive
What kind of memoization does React Compiler add?

Should I try out the compiler?

We encourage everyone to start using React Compiler. While the compiler is still an optional addition to React today, in the future some features may require the compiler in order to fully work.

Is it safe to use?

React Compiler is now stable and has been tested extensively in production. While it has been used in production at companies like Meta, rolling out the compiler to production for your app will depend on the health of your codebase and how well you’ve followed the Rules of React.

What build tools are supported?

React Compiler can be installed across several build tools such as Babel, Vite, Metro, and Rsbuild.

React Compiler is primarily a light Babel plugin wrapper around the core compiler, which was designed to be decoupled from Babel itself. While the initial stable version of the compiler will remain primarily a Babel plugin, we are working with the swc and oxc teams to build first class support for React Compiler so you won’t have to add Babel back to your build pipelines in the future.

Next.js users can enable the swc-invoked React Compiler by using v15.3.1 and up.

What should I do about useMemo, useCallback, and React.memo?

By default, React Compiler will memoize your code based on its analysis and heuristics. In most cases, this memoization will be as precise, or moreso, than what you may have written.

However, in some cases developers may need more control over memoization. The useMemo and useCallback hooks can continue to be used with React Compiler as an escape hatch to provide control over which values are memoized. A common use-case for this is if a memoized value is used as an effect dependency, in order to ensure that an effect does not fire repeatedly even when its dependencies do not meaningfully change.

For new code, we recommend relying on the compiler for memoization and using useMemo/useCallback where needed to achieve precise control.

For existing code, we recommend either leaving existing memoization in place (removing it can change compilation output) or carefully testing before removing the memoization.

Try React Compiler

This section will help you get started with React Compiler and understand how to use it effectively in your projects.

Additional resources

In addition to these docs, we recommend checking the React Compiler Working Group for additional information and discussion about the compiler.

上一篇React Compiler下一篇Installation