Timo Mämecke
bc1c533833
Summary: `window` exists in the React Native runtime, but not inside the test environment. Many libraries use `typeof window === 'undefined'` to check if code is running in SSR. Because of the difference in the real environment and test environment, tests can behave different than the real app, which is an unwanted behavior. ## Background I'm using https://github.com/tannerlinsley/react-query in my React Native Project, which works really well. When writing tests, they wouldn't work: jest started and then seemingly did nothing. While debugging I noticed the render was stuck in an infinite loop. Then I noticed the following line inside `react-query`: ```js const isServer = typeof window === 'undefined' ``` I didn't know that the React Native runtime has a global `window`, and thought it's a bug inside react-query. But it does have a `window`, which is not defined inside the test environment. The infinite loop was caused by react-query thinking it is running on the server, which doesn't fetch any data. If the react-query hook mounts, it re-executes because then it should be mounted inside the client. But `isServer` was still `true`. This repeats forever. ## Changelog [General] [Fixed] - Fix `window` not existing in jest setup Pull Request resolved: https://github.com/facebook/react-native/pull/28067 Test Plan: Are there tests to check if the test environment is setup correctly? � Reviewed By: yungsters Differential Revision: D30317021 Pulled By: charlesbdudley fbshipit-source-id: 837ed952833ef8e70c5132c9b4152b0e0f28b4dd
React Native
Learn once, write anywhere:
Build mobile apps with React.
Getting Started · Learn the Basics · Showcase · Contribute · Community · Support
React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 11.0 and Android 5.0 (API 21) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools, and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in the React Native Community, @react-native-community/react-native-releases.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.