Related
I heard about Hermes, this tool for react native is supposed to make the app faster by converting the JS code into bytecode (Android).
Now my question is: Does this mean that the index.android.bundle in the APK file will contain only bytecode instead of JS code ?
That is correct. One of the features of Hermes is that it reduces TTI by moving JS compilation from runtime to app package build time.
You can verify this by inspecting the contents of your APK.
From the Expo website
Expo lets web developers build truly native apps that work across both iOS and Android by writing them once in just JavaScript.
Isn't this what React Native does? What's the difference?
When you write code in Expo you are writing React Native code. Expo has
two main pieces:
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.
So Expo is a set of tools built on top of React Native. These tools depend on one key belief held at Expo: it's possible to build most apps without ever needing to write native code, provided that you have a comprehensive set of APIs exposed to JavaScript.
This is important because with React Native you can always drop down to native code. This is incredibly helpful sometimes but it comes at a cost: you need to send people your binaries if you want them to test them, someone on the other side of the world can't just tap a link to open it while you're working on it and you can't just publish it with one click for someone to access it similar to how you would in a browser.
With Expo, we suggest that try to avoid dropping down to native code, if you can. As I mentioned above, we think that with a comprehensive set of APIs available to JavaScript, this shouldn't be necessary for most apps. So, we aim to provide this comprehensive set of APIs, and then build all of the awesome tooling that can exist in a world where the native runtime is shared.
However, if you must find that you want to drop down to native, you can use eject and continue using the native APIs that Expo gives you while having the same level of control as you would in any native project.
Read more about ejecting
A summary of the documentation and answers from Expo employees:
React Native init:
Advantages
You can add native modules written in Java or Objective-C (probably the only but the strongest one)
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
Expo
Advantages
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)
Sources:
Detaching Expo Apps to ExpoKit: Concepts
Difference between react-native-init and create-react-native-app #516
Ejecting to ExpoKit
The answer of Brent Vatne is fine, but I'd like to add some details.
Expo expands the API surface of React Native
React Native does not give you all the JavaScript APIs you need out of the box, but only most primitive features. React Native developers are expected to use Android Studio or Xcode to link additional native libraries.
Expo aims to enhance React Native and provide all the JavaScript APIs you need for the most common needs. It is basically a set of well-defined quality native libs already packaged for you in a single lib: ExpoKit. Sometimes these libraries are actually already existing in the React Native world, and integrated into ExpoKit.
It is also important to notice that the Expo team can't include every library out there into ExpoKit (which may create some frustration) because the Hello, World! app size would grow, as it would ship a lot of API's that wouldn't be used in most apps.
Expo provides over-the-air JavaScript updates
Like other systems (CodePush, etc.), Expo provides a system to update your app over the air. This means you upload your JavaScript bundle on a CDN and the mobile apps will automatically download and use the new JavaScript code on next startup (without requesting a publication/review from the stores).
Expo provides a CLI tool to upload/manage the JavaScript bundles on their CDN. For development you can also choose to become the CDN and host the JavaScript bundle on localhost. And Expo XDE is just a visual wrapper on the CLI.
Expo provides a generic client
The Expo client is a generic client that permits to load any app that is compatible with Expo. All the Expo apps do share the exact same native runtime (React Native + ExpoKit). The only difference is the JavaScript code that we give them. The Expo apps you publish to the app stores have your JavaScript bundle URL hardcoded in it. The Expo client is build in a specific way so that you can choose from which URL to load the JS, by scanning a QR code or providing a URL.
Note that this client can also load JavaScript bundles from localhost, and make your development experience easier: There isn't any need for Xcode or Android Studio, and it gets much faster to get your first Hello, World! app running on the phone (from hours to minutes). You can actually develop on an iPhone without a Mac and the setup takes two minutes.
Actually, as the Expo SDK can be upgraded, the Expo client includes a compatibility layer so that it is able to run the last five SDK versions.
Expo provides a build service
As all the Expo apps share the same native code, Expo is able to easily build these apps for you. They have created a cloud build service.
The major thing that differentiate two apps built by Expo is just the hardcoded URL to which the app is supposed to download the JavaScript bundle to run.
Expo does some other things for you, like providing a declarative way to setup app icons, orientations, permissions, API keys, helping you setup push notifications, provisioning profiles... many settings have to be hardcoded at build time in the app and can't be changed over the air.
Expo is to React Native what PhoneGap is to Cordova
React Native is similar Cordova. It is not the same view technology (native vs webview), but both allow you to control native features from JavaScript, and both offer a plugin system so that developers can easily add new JavaScript and native bindings.
PhoneGap is similar to Expo. They both try to enrich the raw API of the underlying platform they are built on with a predefined set of additional native plugins. PhoneGap also offers a build service and has a generic client that work as long as you use the approved plugins.
Conclusion
As you can see, Expo is a set of tools. At the end, it permits to easily develop, share and publish to the stores your mobile projects. It is quite similar to the PhoneGap experience (but a lot better and less confusing).
I will definitively recommend Expo for any new React Native greenfield project, except these two cases:
You already know you need API's that are not available in Expo and won't be anytime soon
You care a lot about your app size (Hello, World! is more than 25 MB due to the large size of ExpoKit, but after that it does not increase much as it is just JavaScript)
It is explained in the official Expo documentation
What is the difference between Expo and React Native?
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.
Expo CLI
Pros:
No need to install Android Studio or Xcode to start building.
Not a lot of configuration required.
Mobile UI to easily view on both Android and iPhone using barcode scanning. Also easier to view with online iPhone and Android simulators.
Faster setup and development.
Cons:
Native dependencies cannot be added.
Creating .apk and .ipa files is difficult.
Size of apk/ipa is huge.
React Native CLI
Pros:
Easily add native dependencies.
Creating .apk and .ipa files is much easier than with Expo
Note: React Native CLI is the framework to use to work directly with the React Native framework.
Cons:
High level of configuration required.
Basic knowledge of Android and iOS folder structure required.
As you can see, both approaches have their pros and cons; you should always decide which to use based on your needs for the project.
The answers about advantages and disadvantages of Expo and React Native CLI are complete. I want to mention another point as my personal experience.
Expo contains many modules by default in the project and it makes easier to work with it. But it has a big problem in the production phase, because the built Android and iOS versions have such a great size. For example, if you have a single page with a 'Hello, World!', the APK file size would be about 19 MB. Having a same project in React Native CLI will result in an app with the size of 6 MB.
So personally I do not recommend using Expo if you want to develop a commercial app.
I would make a note here that Expo is using an older version of React, 16.5, which would prohibit you from using the new hooks feature.
If you decide to go with Expo, be mindful to watch your version controls. Older versions of, say, react-navigation will need to be used with the 16.5 version if you are getting weird errors.
Expo is a wrapper of React Native CLI, which does things under the hood for the ease of developers. The most common problem that Expo solves is that the developer doesn't have to worry about the linking issues of the libraries that often occur in React Native CLI. Expo comes up with tons of libraries now that are extremely helpful for robust development. One of the benefits of Expo is you can develop an app for Android and iOS without having a Mac through Expo mobile application.
As it has tons of benefits, there are some cons of using Expo:
App size increases like hell. A simple Hello, World! app size is more than 30 MB
At times when you need to implement some native functionality into your app, you will need to eject from Expo and go back to React Native CLI. And you can never revert it back to Expo CLI.
I've experienced more than a year that works with Expo.
If the size of the app is not important for you, use Expo because it's easy to implement Map and Push easier than React-native, but at the end of the project, if you want to publish app in Google Play or another store, you have a challenge removing some permissions in your APK.
In React Native you can change everything, but for importing some library, such as push notification or the map, it needs some challenges too, because you have to add these libraries manually to Android and iOS projects.
A summary of the documentation and answers from Expo employees:
React Native init:
Advantages
You can add native modules written in Java or Objective-C (probably the only but the strongest one)
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
Expo
Advantages
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)
Expo and React Native are two popular tools for building mobile apps, but they have some differences. Expo is a free and open-source platform that allows developers to quickly build apps with JavaScript and React Native. It provides a set of tools, libraries, and services that make it easier to get started with building a mobile app. React Native, on the other hand, is a framework for building mobile apps using React. React Native provides a more direct way to access native APIs and components, and allows for more customization and control over the app development process. In summary, Expo provides a faster and easier way to get started with building a mobile app, while React Native provides more control and customization.
Another difference between Expo and React Native is the deployment process. With Expo, you can publish your app directly to the app stores with just a few clicks. You can also take advantage of other services that Expo provides, such as push notifications and authentication. On the other hand, when building a React Native app, you'll need to use tools like Xcode or Android Studio to compile and package the app for deployment. Additionally, you'll have to handle the distribution process yourself, which can be time-consuming and complex.
In terms of performance, React Native generally has better performance compared to Expo as it has a direct access to native APIs and components, whereas Expo relies on its SDK. However, the performance difference may not be significant in many cases.
In conclusion, both Expo and React Native have their own pros and cons, and the choice between them depends on the specific requirements and goals of your project. If you're just starting out with mobile app development and want a fast and easy way to get started, Expo is a great option. However, if you want more control and customization, React Native might be the better choice.
I've recently started react native and following guide on tutorial there are
2 option one is create the project via "create-react-native-app myproject" and other one is "react-native init myproject".
the first one(create-react-native-app) generates app.js only whereas other one generates index.android.js and index.ios.js..
I know somehow they are doing same job but whats the real diffirence here ? which one should I pick to start and when the other one is more usefull over?
The create-react-native-app ("CRNA") CLI builds a project template based on Expo, a third-party toolkit which allows you to write cross-platform React Native applications using only JavaScript, and provides a smoother workflow for getting the app running on a real device. In addition, Expo provides access to tons of native APIs, for which you'd normally need libraries or custom native code.
Expo is great, and in an ideal world, it is what most app developers would probably prefer to use, but Expo's architecture sets an unfortunate limitation: You cannot write custom Native Modules, or integrate third-party libraries which depend on custom native code that isn't build into Expo. This means you have only access to the native functionality provided by React Native and Expo, and cannot easily extend it.
By contrast, the react-native CLI's init command creates a plain React Native app template, with native iOS and Android projects you can modify. The downside of this approach is that you'll need to set up the native iOS and Android build chains on your computer, and it's significantly more cumbersome to get started developing and deploying your app.
Luckily, Expo provides a way to detach a CRNA app from their native app shell. This will convert a CRNA project into something similar to the plain project created by react-native init, but with access to all the Expo SDK functionality.
In practice, the best approach for most beginners and new projects is to start with create-react-native-app, and evaluate whether you'll need to detach later. Expo provides a handy guide to help making that decision.
Can you use libraries like https://github.com/tolu360/react-native-google-places in an Expo project? I assume any npm library is ok to add, but what about libraries like this google places picker that requires post install steps to link the native projects. Are they supported with Expo?
Regular Expo projects are written only in JavaScript and don't support npm packages that contain Objective-C or Java. However, Expo provides an advanced SDK called ExpoKit for when you absolutely need to use custom native code. From the Expo docs:
Normally, Expo apps are written in pure JS and never “drop down”
to the native iOS or Android layer. This is core to the Expo
philosophy and it’s part of what makes Expo fast and powerful to
use.
However, there are some cases where advanced developers need native
capabilities outside of what Expo offers out-of-the-box. The most
common situation is when a project requires a specific Native Module
which is not supported by React Native Core or the Expo SDK.
You could "detach" your Expo project to create Xcode and Android Studio projects that contain ExpoKit. Then you would add custom Objective-C or Java the same way as with any other Xcode or Android Studio project.
However, the Expo docs also warn about some of the downsides of writing custom native code; many features often can be implemented well in JS, allowing you to retain all of the benefits of a standard Expo project.
Warning: We discourage most of our developers from taking this route,
as we believe almost everything you need to do is better accomplished
in a cross-platform way with JS.
Writing in JS enables you to best take advantage of over-the-air code
deployment and benefit from ongoing updates and support from Expo.
You should only do this if you have a particular demand from native
code which Expo won’t do a good job supporting, such as (for
example) specialized CPU-intensive video processing that must happen
locally on the device.
From the Expo website
Expo lets web developers build truly native apps that work across both iOS and Android by writing them once in just JavaScript.
Isn't this what React Native does? What's the difference?
When you write code in Expo you are writing React Native code. Expo has
two main pieces:
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.
So Expo is a set of tools built on top of React Native. These tools depend on one key belief held at Expo: it's possible to build most apps without ever needing to write native code, provided that you have a comprehensive set of APIs exposed to JavaScript.
This is important because with React Native you can always drop down to native code. This is incredibly helpful sometimes but it comes at a cost: you need to send people your binaries if you want them to test them, someone on the other side of the world can't just tap a link to open it while you're working on it and you can't just publish it with one click for someone to access it similar to how you would in a browser.
With Expo, we suggest that try to avoid dropping down to native code, if you can. As I mentioned above, we think that with a comprehensive set of APIs available to JavaScript, this shouldn't be necessary for most apps. So, we aim to provide this comprehensive set of APIs, and then build all of the awesome tooling that can exist in a world where the native runtime is shared.
However, if you must find that you want to drop down to native, you can use eject and continue using the native APIs that Expo gives you while having the same level of control as you would in any native project.
Read more about ejecting
A summary of the documentation and answers from Expo employees:
React Native init:
Advantages
You can add native modules written in Java or Objective-C (probably the only but the strongest one)
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
Expo
Advantages
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)
Sources:
Detaching Expo Apps to ExpoKit: Concepts
Difference between react-native-init and create-react-native-app #516
Ejecting to ExpoKit
The answer of Brent Vatne is fine, but I'd like to add some details.
Expo expands the API surface of React Native
React Native does not give you all the JavaScript APIs you need out of the box, but only most primitive features. React Native developers are expected to use Android Studio or Xcode to link additional native libraries.
Expo aims to enhance React Native and provide all the JavaScript APIs you need for the most common needs. It is basically a set of well-defined quality native libs already packaged for you in a single lib: ExpoKit. Sometimes these libraries are actually already existing in the React Native world, and integrated into ExpoKit.
It is also important to notice that the Expo team can't include every library out there into ExpoKit (which may create some frustration) because the Hello, World! app size would grow, as it would ship a lot of API's that wouldn't be used in most apps.
Expo provides over-the-air JavaScript updates
Like other systems (CodePush, etc.), Expo provides a system to update your app over the air. This means you upload your JavaScript bundle on a CDN and the mobile apps will automatically download and use the new JavaScript code on next startup (without requesting a publication/review from the stores).
Expo provides a CLI tool to upload/manage the JavaScript bundles on their CDN. For development you can also choose to become the CDN and host the JavaScript bundle on localhost. And Expo XDE is just a visual wrapper on the CLI.
Expo provides a generic client
The Expo client is a generic client that permits to load any app that is compatible with Expo. All the Expo apps do share the exact same native runtime (React Native + ExpoKit). The only difference is the JavaScript code that we give them. The Expo apps you publish to the app stores have your JavaScript bundle URL hardcoded in it. The Expo client is build in a specific way so that you can choose from which URL to load the JS, by scanning a QR code or providing a URL.
Note that this client can also load JavaScript bundles from localhost, and make your development experience easier: There isn't any need for Xcode or Android Studio, and it gets much faster to get your first Hello, World! app running on the phone (from hours to minutes). You can actually develop on an iPhone without a Mac and the setup takes two minutes.
Actually, as the Expo SDK can be upgraded, the Expo client includes a compatibility layer so that it is able to run the last five SDK versions.
Expo provides a build service
As all the Expo apps share the same native code, Expo is able to easily build these apps for you. They have created a cloud build service.
The major thing that differentiate two apps built by Expo is just the hardcoded URL to which the app is supposed to download the JavaScript bundle to run.
Expo does some other things for you, like providing a declarative way to setup app icons, orientations, permissions, API keys, helping you setup push notifications, provisioning profiles... many settings have to be hardcoded at build time in the app and can't be changed over the air.
Expo is to React Native what PhoneGap is to Cordova
React Native is similar Cordova. It is not the same view technology (native vs webview), but both allow you to control native features from JavaScript, and both offer a plugin system so that developers can easily add new JavaScript and native bindings.
PhoneGap is similar to Expo. They both try to enrich the raw API of the underlying platform they are built on with a predefined set of additional native plugins. PhoneGap also offers a build service and has a generic client that work as long as you use the approved plugins.
Conclusion
As you can see, Expo is a set of tools. At the end, it permits to easily develop, share and publish to the stores your mobile projects. It is quite similar to the PhoneGap experience (but a lot better and less confusing).
I will definitively recommend Expo for any new React Native greenfield project, except these two cases:
You already know you need API's that are not available in Expo and won't be anytime soon
You care a lot about your app size (Hello, World! is more than 25 MB due to the large size of ExpoKit, but after that it does not increase much as it is just JavaScript)
It is explained in the official Expo documentation
What is the difference between Expo and React Native?
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.
Expo CLI
Pros:
No need to install Android Studio or Xcode to start building.
Not a lot of configuration required.
Mobile UI to easily view on both Android and iPhone using barcode scanning. Also easier to view with online iPhone and Android simulators.
Faster setup and development.
Cons:
Native dependencies cannot be added.
Creating .apk and .ipa files is difficult.
Size of apk/ipa is huge.
React Native CLI
Pros:
Easily add native dependencies.
Creating .apk and .ipa files is much easier than with Expo
Note: React Native CLI is the framework to use to work directly with the React Native framework.
Cons:
High level of configuration required.
Basic knowledge of Android and iOS folder structure required.
As you can see, both approaches have their pros and cons; you should always decide which to use based on your needs for the project.
The answers about advantages and disadvantages of Expo and React Native CLI are complete. I want to mention another point as my personal experience.
Expo contains many modules by default in the project and it makes easier to work with it. But it has a big problem in the production phase, because the built Android and iOS versions have such a great size. For example, if you have a single page with a 'Hello, World!', the APK file size would be about 19 MB. Having a same project in React Native CLI will result in an app with the size of 6 MB.
So personally I do not recommend using Expo if you want to develop a commercial app.
I would make a note here that Expo is using an older version of React, 16.5, which would prohibit you from using the new hooks feature.
If you decide to go with Expo, be mindful to watch your version controls. Older versions of, say, react-navigation will need to be used with the 16.5 version if you are getting weird errors.
Expo is a wrapper of React Native CLI, which does things under the hood for the ease of developers. The most common problem that Expo solves is that the developer doesn't have to worry about the linking issues of the libraries that often occur in React Native CLI. Expo comes up with tons of libraries now that are extremely helpful for robust development. One of the benefits of Expo is you can develop an app for Android and iOS without having a Mac through Expo mobile application.
As it has tons of benefits, there are some cons of using Expo:
App size increases like hell. A simple Hello, World! app size is more than 30 MB
At times when you need to implement some native functionality into your app, you will need to eject from Expo and go back to React Native CLI. And you can never revert it back to Expo CLI.
I've experienced more than a year that works with Expo.
If the size of the app is not important for you, use Expo because it's easy to implement Map and Push easier than React-native, but at the end of the project, if you want to publish app in Google Play or another store, you have a challenge removing some permissions in your APK.
In React Native you can change everything, but for importing some library, such as push notification or the map, it needs some challenges too, because you have to add these libraries manually to Android and iOS projects.
A summary of the documentation and answers from Expo employees:
React Native init:
Advantages
You can add native modules written in Java or Objective-C (probably the only but the strongest one)
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
Expo
Advantages
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)
Expo and React Native are two popular tools for building mobile apps, but they have some differences. Expo is a free and open-source platform that allows developers to quickly build apps with JavaScript and React Native. It provides a set of tools, libraries, and services that make it easier to get started with building a mobile app. React Native, on the other hand, is a framework for building mobile apps using React. React Native provides a more direct way to access native APIs and components, and allows for more customization and control over the app development process. In summary, Expo provides a faster and easier way to get started with building a mobile app, while React Native provides more control and customization.
Another difference between Expo and React Native is the deployment process. With Expo, you can publish your app directly to the app stores with just a few clicks. You can also take advantage of other services that Expo provides, such as push notifications and authentication. On the other hand, when building a React Native app, you'll need to use tools like Xcode or Android Studio to compile and package the app for deployment. Additionally, you'll have to handle the distribution process yourself, which can be time-consuming and complex.
In terms of performance, React Native generally has better performance compared to Expo as it has a direct access to native APIs and components, whereas Expo relies on its SDK. However, the performance difference may not be significant in many cases.
In conclusion, both Expo and React Native have their own pros and cons, and the choice between them depends on the specific requirements and goals of your project. If you're just starting out with mobile app development and want a fast and easy way to get started, Expo is a great option. However, if you want more control and customization, React Native might be the better choice.