2a7e02edf6
Summary: This diff fixes an issue that caused the problem with `regeneratorRuntime` last Friday (more info: https://fb.facebook.com/groups/frontendsupport/permalink/2427883350560427/). The root issue is that both `InitializeCore` and `FBInitializeCore` are included in the same bundle, this fix just prevents the bundle from being invalid once this happens.. *copied from: https://our.intern.facebook.com/intern/diff/D10444264/?transaction_id=595485237532887* The way that `regeneratorRuntime` is polyfilled is not correct: ``` polyfillGlobal('regeneratorRuntime', () => { // The require just sets up the global, so make sure when we first // invoke it the global does not exist delete global.regeneratorRuntime; require('regenerator-runtime/runtime'); return global.regeneratorRuntime; }); ``` Since a `require`d module is only evaluated once (no matter how many times it's required), defining (and calling) a getter for `global.regeneratorRuntime` twice will end up storing `undefined` to `global.regeneratorRuntime`. There were no issues before this diff because the ordering of requires made things work by coincidence, e.g the following code will work: ``` // Set up regenerator for the first time polyfillGlobal('regeneratorRuntime', () => { delete global.regeneratorRuntime; require('regenerator-runtime/runtime'); return global.regeneratorRuntime; }); // Set up regenerator for the second time. This will just override the previous getter (which has not even got executed so // the `regenerator-runtime/runtime` module has not been evaluated yet. polyfillGlobal('regeneratorRuntime', () => { // The require just sets up the global, so make sure when we first // invoke it the global does not exist delete global.regeneratorRuntime; require('regenerator-runtime/runtime'); return global.regeneratorRuntime; }); // Now access regenerator global.regeneratorRuntime; ``` But the following code won't work: ``` // Set up regenerator for the first time polyfillGlobal('regeneratorRuntime', () => { delete global.regeneratorRuntime; require('regenerator-runtime/runtime'); return global.regeneratorRuntime; }); // Access regenerator. This will cause the previous getter to be called, and the `regenerator-runtime/runtime` module will get evaluated. // Here, `global.regeneratorRuntime` will have a correct value. global.regeneratorRuntime; // Set up regenerator for the second time. This will define a new getter for `global.regeneratorRuntime`, which will delete `delete global.regeneratorRuntime` // and return undefined (note that `require('regenerator-runtime/runtime');` is a noop since the module has been already evaluated). polyfillGlobal('regeneratorRuntime', () => { // The require just sets up the global, so make sure when we first // invoke it the global does not exist delete global.regeneratorRuntime; require('regenerator-runtime/runtime'); return global.regeneratorRuntime; }); ``` Reviewed By: fromcelticpark Differential Revision: D10483975 fbshipit-source-id: 5b3ef6e11c4fc4f79e3857c1ade9e7bc2beb6a39
React Native · 
Learn once, write anywhere: Build mobile apps with React.
See the official React Native website for an introduction to React Native.
Requirements
Supported target operating systems are >= Android 4.1 (API 16) and >= iOS 9.0. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS by default (tools like Expo can be used to get 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:
How React Native works
React Native lets you build mobile apps using JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.
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, Kotlin, 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.
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.
React Native combines smoothly with components written in Objective-C, Java, Kotlin, 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.
Full documentation
The full documentation for React Native can be found on our website. The source for the React Native documentation and website is hosted on a separate repo, https://github.com/facebook/react-native-website.
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.
Join the React Native community
- Website: https://facebook.github.io/react-native
- Twitter: https://twitter.com/reactnative
- Discussion: https://discuss.reactjs.org/
See the CONTRIBUTING file for how to help out.
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.