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React
playground.react.dev
React Compiler Playground
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Playcode
playcode.io › react
React Playground - Online React Editor & Compiler Free
3 weeks ago - Free React playground to build and test React apps online. Live preview, hot reloading, npm packages, and JSX support. No setup required, start coding React instantly.
Discussions

Introducing React Compiler – React
One ever present debate in the React community had been whether you should `useMemo`/`useCallback` all non-primitive props or not. I've often taken the position that you should in real world teams because it's too much work to determine exactly when to otherwise , whereas others argue that it's too much runtime overhead (and noise) and not worth it. u/acemarke has a good summary of the arguments . All that to say, I was curious if this compiler is essentially the React team conceding that you _should_ memoize everything. The answer is pretty interesting - the compiler actually memoizes things in a more efficient way than `useMemo` can . So it's almost the best of all worlds: improved rendering performance from memoization, cheaper memoization cost, and none of the noise of `useMemo`s sprinkled everywhere. I think we'll have to wait a bit longer to see if this works out in practice, and I'm not crazy about having to add another layer of transpilation, but if it works well this will be a pretty big win for React projects in general I think. More on reddit.com
🌐 r/reactjs
56
308
May 15, 2024
I built a code playground to visualise complex engineering flows.
Hey folks! This is something that I have been working on for a few months.  It's a browser based "runtime" where you write code, the compiler transforms it, and the runtime executes it visually. I built this because I hate designing software/systems in http://lucid.io/ and even the new age tools like http://eraser.io/ . The diagrams are too static and the solution too cookie-cutter. React has been a life saver honestly. Since I come from a backend background, I really needed something with an established ecosystem and something that just clicks! Every major component that I needed to pull it off, be it the IDE, state-management or actually visualising, had amazing react support. I don't think this would have been possible for me in any other ecosystem to learn this quickly and build. Here’s how it works internally: Users write class-based code, and my compiler applies my custom transformers while building the code. The transformation is simple but rigorous. It converts methods and other surrounding functions into `AsyncGenerators`, essentially something that can pause execution. With this step we convert the code into state-machines. We have a bare bones runtime, along with a heap and stack. Any object that gets created, also gets registered on the heap. And any method call that happens, gets recorded on the stack. Then we simply let things play out and render the heap and stack. This rendering is performed on https://reactflow.dev/ Here are some examples you can try right away: Here's a medium level example involving an event stream of stock prices and a system calculating its running avarage. https://app.metz.sh/template/7 Here's something a bit more complex and more real. This one is about a polling setup with multiple pollers interacting with databases. https://app.metz.sh/template/4 And this last one is my favourite and of the reason I built it. It's about a payment system which books two entries for the same payment. This one is personal since I made the same mistake a few years ago which led to an actual loss of money! https://app.metz.sh/play/0286b754d9e4408ba172e344eeac47b9 Github: https://github.com/metz-sh/simulacrum Playground: https://try.metz.sh Docs: https://docs.metz.sh More on reddit.com
🌐 r/reactjs
1
24
May 21, 2024
New comprehensive React Compiler docs released!
thanks for posting! please let me know if anything is unclear or any other general feedback More on reddit.com
🌐 r/reactjs
21
137
May 24, 2025
TypeScript Playground with React Support
Great thang. More on reddit.com
🌐 r/reactjs
1
7
April 26, 2020
People also ask

Can I use npm packages in the online compiler?
Yes! PlayCode supports the entire npm ecosystem. Just import any package like React, Vue, Lodash, or Axios, and our compiler fetches and bundles it automatically. No npm install needed. Our intelligent caching makes subsequent imports instant.
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playcode.io
playcode.io › javascript-compiler
JavaScript Compiler - AI-Powered JS Compiler Online | Free
What is a JavaScript compiler?
A JavaScript compiler transforms your JavaScript code into optimized, executable code. Unlike traditional compilers that produce machine code, JS compilers like PlayCode bundle your code, resolve imports, and transpile modern syntax (ES2026, TypeScript, JSX) into browser-compatible JavaScript that runs instantly.
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playcode.io
playcode.io › javascript-compiler
JavaScript Compiler - AI-Powered JS Compiler Online | Free
Is PlayCode's JavaScript compiler free?
Yes, PlayCode's JavaScript compiler is completely free to use. You can compile and run unlimited JavaScript code, use npm packages, and see live preview results without paying anything. Pro features like AI assistance and private projects are available for subscribers.
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playcode.io
playcode.io › javascript-compiler
JavaScript Compiler - AI-Powered JS Compiler Online | Free
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Vercel
reactplayground.vercel.app
React Playground
URL-based React Playground. Craft, experiment, and collaborate with ease using our sandbox. Build, test, and share your concepts hassle-free. No need for sign-in: your creations are stored directly in the URL.
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Playcode
playcode.io › javascript-compiler
JavaScript Compiler - AI-Powered JS Compiler Online | Free
18 hours ago - For a sandbox experience with live preview, try our JavaScript Playground. Our JavaScript compiler supports the latest ECMAScript 2024 features, TypeScript with full type checking, and JSX/TSX for React development.
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NextLeap
nextleap.app › online-compiler › reactjs-programming
React Online Compiler | Code, Compile, and Debug React Apps - NextLeap
Experience the power of React with NextLeap's Online Compiler. Write, compile, and debug React applications online in real-time. Boost your productivity and enhance your React development workflow with our intuitive platform.
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InfoQ
infoq.com › news › 2025 › 12 › react-compiler-meta
Meta's React Compiler 1.0 Brings Automatic Memoization to Production - InfoQ
2 days ago - 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. The compiler has been battle tested on major applications at Meta and is ...
Find elsewhere
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CodeSandbox
codesandbox.io › s › react-compiler-vgbeg
React Compiler - CodeSandbox
December 16, 2019 - React Compiler by mf4lsb using react, react-bootstrap, react-dom, react-scripts
Published   Dec 13, 2019
Author   mf4lsb
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OneCompiler
onecompiler.com › react
ReactJS Online Editor & Compiler
Write, Run & Share React code online using OneCompiler's React online compiler for free. It’s one of the simplest yet powerful React playgrounds running on the latest React version 18. Getting started with OneCompiler’s React editor is easy and fast.
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StackBlitz
stackblitz.com › edit › react-playground-practice
React Playground Practice - StackBlitz
Starter project for React apps that exports to the create-react-app CLI.
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GitHub
github.com › Lemoncode › react-compiler-playground
GitHub - Lemoncode/react-compiler-playground: Just some simple test to check react compiler in action
Description: We test whether the compiler optimizes expensive calculations previously wrapped in useMemo. ✅ The compiler handles simple memoization cases without requiring useMemo.
Author   Lemoncode
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JSFiddle
jsfiddle.net › boilerplate › react-jsx
React - JSFiddle - Code Playground
JSFiddle - Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle.
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Playcode
playcode.io › react_ts_hooks
React TypeScript Hooks
PlayCode's JS sandbox supports modern ES features, TypeScript, React, Vue, and more. Whether you're learning JavaScript, testing ideas, or building prototypes, our code playground is the fastest way to go from idea to working code. Need to compile and run JavaScript code?
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React
react.dev › learn › react-compiler
React Compiler – React
Learn strategies for gradually adopting React Compiler in your existing codebase if you’re not ready to enable it everywhere yet.
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CodeSandbox
codesandbox.io › s › react-new
React - CodeSandbox
December 6, 2024 - React example starter project
Published   Apr 01, 2017
Author   CompuIves
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Expo Documentation
docs.expo.dev › guides › react-compiler
React Compiler - Expo Documentation
November 3, 2025 - To better understand how React Compiler works, check out the React Playground.
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TypeScript
typescriptlang.org › play
TS Playground - An online editor for exploring ...
The Playground lets you write TypeScript or JavaScript online in a safe and sharable way.
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GitHub
github.com › reactwg › react-compiler › discussions › 5
Introducing React Compiler · reactwg/react-compiler · Discussion #5
React Compiler is a new build-time tool that automatically optimizes your React app to improve its performance, particularly on updates (re-renders). The compiler is designed to work with existing ...
Author   reactwg
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React
react.dev
React
React is the library for web and native user interfaces. Build user interfaces out of individual pieces called components written in JavaScript. React is designed to let you seamlessly combine components written by independent people, teams, ...
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CodeChef
codechef.com › ide
Online Compiler & IDE for Python, C++, C, Java, Rust - CodeChef
Compile & run your code with the CodeChef online IDE. Our online compiler supports multiple programming languages like Python, C++, C, JavaScript, Rust, Go, Kotlin, and many more.
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StackBlitz
stackblitz.com › fork › react
React
A create-react-app project based on react and react-dom.