当你在Expo中编写代码时，你就是在编写React Native代码。世博会已经 两个主要部分:

Expo CLI (expo-cli): a developer tool for creating projects, viewing logs, opening on your device, publishing, etc. Expo client: an app on your phone that lets you open your projects while you're working on them, without needing to go through XCode or Android Studio, and also lets other people view them too! And if you publish it through expo-cli, people can access it at any time through the Expo client on Android or on iOS if signed in to the same account it was published with. Lastly, we also make it possible to build standalone apps so people don't have to use the Expo client to open it, and you can distribute to the app store and play store if you like.

所以Expo是建立在React Native之上的一套工具。这些工具依赖于Expo上的一个关键信念:只要你有一套全面的面向JavaScript的api，就可以构建大多数应用程序，而不需要编写本地代码。

这一点很重要，因为使用React Native，你总是可以下拉到本地代码。这有时是非常有用的，但它是有代价的:如果你想让他们测试你的二进制文件，你需要把你的二进制文件发给他们，世界另一边的人不能在你工作的时候点击一个链接来打开它，你不能像在浏览器中那样一键发布它，让别人访问它。

对于Expo，我们建议尽量避免使用本地代码，如果可以的话。正如我上面提到的，我们认为JavaScript有了一套全面的api，对于大多数应用程序来说，这应该是不必要的。因此，我们的目标是提供这个全面的api集，然后构建所有可以存在于本机运行时共享世界中的强大工具。

但是，如果你必须发现你想要下拉到本地，你可以使用eject并继续使用Expo提供给你的本地api，同时拥有与任何本地项目相同的控制级别。

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当你在Expo中编写代码时，你就是在编写React Native代码。世博会已经 两个主要部分:

Expo CLI (expo-cli): a developer tool for creating projects, viewing logs, opening on your device, publishing, etc. Expo client: an app on your phone that lets you open your projects while you're working on them, without needing to go through XCode or Android Studio, and also lets other people view them too! And if you publish it through expo-cli, people can access it at any time through the Expo client on Android or on iOS if signed in to the same account it was published with. Lastly, we also make it possible to build standalone apps so people don't have to use the Expo client to open it, and you can distribute to the app store and play store if you like.

所以Expo是建立在React Native之上的一套工具。这些工具依赖于Expo上的一个关键信念:只要你有一套全面的面向JavaScript的api，就可以构建大多数应用程序，而不需要编写本地代码。

这一点很重要，因为使用React Native，你总是可以下拉到本地代码。这有时是非常有用的，但它是有代价的:如果你想让他们测试你的二进制文件，你需要把你的二进制文件发给他们，世界另一边的人不能在你工作的时候点击一个链接来打开它，你不能像在浏览器中那样一键发布它，让别人访问它。

对于Expo，我们建议尽量避免使用本地代码，如果可以的话。正如我上面提到的，我们认为JavaScript有了一套全面的api，对于大多数应用程序来说，这应该是不必要的。因此，我们的目标是提供这个全面的api集，然后构建所有可以存在于本机运行时共享世界中的强大工具。

但是，如果你必须发现你想要下拉到本地，你可以使用eject并继续使用Expo提供给你的本地api，同时拥有与任何本地项目相同的控制级别。

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在世博会的官方文件中有解释

Expo和React Native的区别是什么?

Expo is kind of like Rails for React Native. Lots of things are set up for you, so it’s quicker to get started and on the right path. With Expo, you don’t need Xcode or Android Studio. You just write JavaScript using whatever text editor you are comfortable with (Atom, vim, emacs, Sublime, VS Code, whatever you like). You can run XDE (our desktop software) on Mac, Windows, and Linux. Here are some of the things Expo gives you out of the box that work right away: Support for iOS and Android You can use apps written in Expo on both iOS and Android right out of the box. You don’t need to go through a separate build process for each one. Just open any Expo app in the Expo Client app from the App Store on either iOS or Android (or in a simulator or emulator on your computer). Push Notifications Push notifications work right out of the box across both iOS and Android, using a single, unified API. You don’t have to set up APNS and GCM/FCM or configure ZeroPush or anything like that. We think we’ve made this as easy as it can be right now. Facebook Login This can take a long time to get set up properly yourself, but you should be able to get it working in 10 minutes or less on Expo. Instant Updating All Expo apps can be updated in seconds by just clicking Publish in XDE. You don’t have to set anything up; it just works this way. If you aren’t using Expo, you’d either use Microsoft Code Push or roll your own solution for this problem Asset Management Images, videos, fonts, etc. are all distributed dynamically over the Internet with Expo. This means they work with instant updating and can be changed on the fly. The asset management system built-in to Expo takes care of uploading all the assets in your repo to a CDN so they’ll load quickly for anyone. Without Expo, the normal thing to do is to bundle your assets into your app which means you can’t change them. Or you’d have to manage putting your assets on a CDN or similar yourself. Easier Updating To New React Native Releases We do new releases of Expo every few weeks. You can stay on an old version of React Native if you like, or upgrade to a new one, without worrying about rebuilding your app binary. You can worry about upgrading the JavaScript on your own time. But no native modules… The most limiting thing about Expo is that you can’t add in your own native modules without detaching and using ExpoKit.

我在世博工作了一年多。 如果应用的大小对你来说不重要，使用Expo，因为它比React-native更容易实现Map和Push，但在项目结束时，如果你想在谷歌Play或其他商店发布应用，你会遇到一个挑战，删除APK中的一些权限。

在React Native中，你可以改变一切，但对于导入一些库，如推送通知或地图，它也需要一些挑战，因为你必须手动将这些库添加到Android和iOS项目中。

世博员工的回答和文件摘要:

React Native init: 优势

您可以添加用Java或Objective-C(可能是唯一但也是最强的一种)编写的本机模块。

Disadvantages Needs Android Studio and Xcode to run the projects You can't develop for iOS without having a Mac Device has to be connected via USB to use it for testing Fonts need to be imported manually in Xcode If you want to share the app you need to send the whole .apk / .ipa file Does not provide JavaScript APIs out of the box, e.g., Push-Notifications, Asset Manager, they need to be manually installed and linked with npm for example Setting up a working project properly (including device configuration) is rather complicated and can take time

世博会 优势

Setting up a project is easy and can be done in minutes You (and other people) can open the project while you're working on it Sharing the app is easy (via a QR code or link), you don't have to send the whole .apk or .ipa file No build necessary to run the app Integrates some basic libraries in a standard project (Push Notifications, Asset Manager, etc.) You can eject it to ExpoKit and integrate native code continuing using some of the Expo features, but not all of them Expo can build .apk and .ipa files (distribution to stores possible with Expo)

Disadvantages You can't add native modules (probably a game changer for some) You can't use libraries that use native code in Objective-C/Java The standard Hello World app is about 25MB big (because of the integrated libraries) If you want to use: FaceDetector, ARKit, or Payments you need to eject it to ExpoKit Ejecting it to ExpoKit has a trade-off of features of Expo, e.g. you cannot share via a QR code When ejecting to ExpoKit you are limited to the react-native version that is supported by ExpoKit then Debugging in ExpoKit (with native modules) is a lot more complicated, since it mixes two languages and different libraries (no official Expo support any more)

这里我要说明的是，Expo使用的是React的旧版本16.5，这将禁止你使用新的hooks功能。

如果您决定使用Expo，请注意您的版本控制。例如，如果遇到奇怪的错误，就需要在16.5版本中使用旧版本的反应导航。