165b38ab7a
Summary: This usage of `...` currently causes BackHandler to silently become non-functional when a `Symbol` polyfill is used. Why? - The `[...obj]` operator implicitly calls the object's iterator to fill the array - react-native's internal `Set` polyfill has a load order issue that breaks it whenever a project uses a `Symbol` polyfill - This means that when `BackHandler` tries to `[...set]` a `Set` of subscriptions the result is always an empty array instead of an array of subscriptions Additionally it's worth noting that the current code is also wastefully inefficient as in order to reverse iterate over subscriptions it: - Clones the `Set` (which fills it by implicitly running the set's iterator) - Uses `[...set]` to convert the cloned set into an array (which also implicitly runs the iterator on the clone) - Finally reverses the order of the array ---- This code fixes this problem by replacing the use of multiple Set instance iterators with a simple `.forEach` loop that unshifts directly into the final array. I've tested this by opening the repo's RNTester app on Android and tvOS ensuring that the back handler works before changes, the application crashes when I introduce an error (to verify my code changes are being applied to the app), the back handler works and after changes. Fixes #11968 Closes https://github.com/facebook/react-native/pull/15182 Differential Revision: D6114696 Pulled By: hramos fbshipit-source-id: 2eae127558124a394bb3572a6381a5985ebf9d64 |
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README.md
React Native · 
Learn once, write anywhere: Build mobile apps with React.
- Build native mobile apps using JavaScript and React: React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.
- A React Native app is a real mobile app: With React Native, you don't build a "mobile web app", an "HTML5 app", or a "hybrid app". You build a real mobile app that's indistinguishable from an app built using Objective-C, Java, or Swift. React Native uses the same fundamental UI building blocks as regular iOS and Android apps. You just put those building blocks together using JavaScript and React.
- Don't waste time recompiling: React Native lets you build your app faster. Instead of recompiling, you can reload your app instantly. With hot reloading, you can even run new code while retaining your application state. Give it a try - it's a magical experience.
- Use native code when you need to: React Native combines smoothly with components written in Objective-C, Java, or Swift. It's simple to drop down to native code if you need to optimize a few aspects of your application. It's also easy to build part of your app in React Native, and part of your app using native code directly - that's how the Facebook app works.
The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
See the official React Native website for an introduction to React Native.
Supported operating systems are >= Android 4.1 (API 16) and >= iOS 8.0.
Getting Started
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 website’s documentation is divided into multiple sections.
- There are Guides that discuss topics like debugging, integrating with existing apps, and the gesture responder system.
- The Components section covers React components such as
ViewandButton. - The APIs section covers other libraries like Animated and StyleSheet that aren’t React components themselves.
- Finally, React Native provides a small number of Polyfills that offer web-like APIs.
Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the Libraries/Components directory for components like ScrollView and TextInput, for example. The RNTester example is also here to demonstrate some of the ways to use these components. From the source you can get an accurate understanding of each component’s behavior and API.
The React Native documentation only discusses the components, APIs and topics specific to React Native (React on iOS and Android). For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
Upgrading
React Native is under active development. See the guide on upgrading React Native to keep your project up-to-date.
Contributing
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 bug fixes and improvements, and how to build and test your changes to React Native.
Beginner Friendly Bugs
We have a list of beginner friendly issues to help you get your feet wet in the React Native codebase and familiar with our contribution process. This is a great place to get started.
License
React Native is BSD licensed. We also provide an additional patent grant.
React Native documentation is Creative Commons licensed.