Exponent – Build native apps in JS that work across both iOS and Android

I wonder why we don't hear that much about them in HN.

https://www.nativescript.org/

> if you have native libraries for x86 or arm 64 in your app it immediately breaks it completely

We handle all the native code for you, so you'll never hit this.

> half the examples and half the dependencies on the web out there crash immediately because they decided you have to import React and Component from "react" instead of "react-native" now

We support multiple React Native versions in our client app, so if you target an old version of React Native it'll keep running on that version even when we upgrade.

The redux 3 vs. 4 part is still an issue, but you should only hit it when you're specifically upgrading your app.

Calling shenanigans given that redux 4 is completely supported and has been supported for a while. Was this many months ago?

One thing I've learned from working with React Native is that you want to stay fairly up to date with the frequent releases. The Exponent team puts a lot of work into upgrading our own dependencies and maintaining the Exponent API that other developers depend on.

Authors of components and other npm packages will update their code to work with the latest version of React Native. It takes energy to stay up to date since you need to read the release notes and breaking changes and sometimes it's helpful to scan the commit history on the release branch. But this way you can use react-redux v4 and other actively developed dependencies.

On the other hand, though, sometimes component authors don't maintain their projects or support one platform but not the other. When dependencies fall out of date there isn't an easy answer. In the past I've fixed the issues myself and sent pull requests. Showing financial support is also another approach; my teammate Brent wrote a post about this: https://blog.getexponent.com/putting-your-money-where-your-p.... The maintenance of open-source libraries isn't unique to React Native but it's perhaps exacerbated by its cross-platform nature and frequent release cycle.

For the issue about CPU ABIs, I believe React Native supports armeabi-v7a and x86 but not arm64-v8a or x64. It would be great to have native arm64 support but so far no one has needed it enough to implement it instead of using ndk.abiFilters. For what it's worth, this works for Exponent and several other companies with apps that use React Native like Facebook.

I honestly struggle to find the problem addressed by RN, at least if you already know java.

- Fork the Exponent client and add your native API.

- Try to get a patch into upstream.

- If it's not urgent, ask us if we plan to implement it and if it seems like a common enough use case we would add it to our roadmap.

- Go into the Exponent source and copy whatever native code you need into a new React Native project.

We're also working on a way to "eject" from Exponent similar to the create-react-app eject command but easier to reverse and to keep receiving updates to Exponent, because it's not an "all-in" kind of eject, you can read more about that here: https://blog.getexponent.com/answered-on-slack-ejecting-from... (caveat: this feature is still in early development)

Here's a video of a talk explaining how the game works: https://www.youtube.com/watch?v=2_KV7Ha_gRk

The game runs on Exponent and uses React Native for rendering (as all Exponent apps do). It uses individual `Image` components for each sprite. This gets choppy when you have a lot of sprites so we're experimenting with more performant ways of rendering for games.

Exponent exposes all of the React Native built-in APIs which encompass a lot of what you're asking about.

For example, here is the Clipboard API: https://facebook.github.io/react-native/docs/clipboard.html

Wifi network configuration is more complicated, but there are some things exposed like "NetInfo" which lets you know the current state of connectivity. https://facebook.github.io/react-native/docs/netinfo.html

The complete React Native docs are here: https://facebook.github.io/react-native/ and Exponent specific docs are here: http://docs.getexponent.com/

For now, Exponent just lets you write things that only use JS, and we make that easy and reliable and straightforward. We actually think this is the best way to write most apps that can be built this way since the code is easier to maintain and works cross platform, and you can do things like instant updates much more reliably when all your code is JS.

We're looking at a way you can write Java/Swift/Obj-C extensions for Exponent, but that will take us some time.

With Exponent you write just JavaScript. In addition to most of the APIs that come with React Native, Exponent provides several APIs (https://docs.getexponent.com/versions/latest/sdk/index.html) and we're steadily adding more. If there's a native API we don't have yet that developers need, they tell us about it and we add it to our roadmap.

Exponent is open-source, too, so if you needed to you could fork it and write your own native code or make a raw React Native app. We recommend writing pure JS apps if you can, though. At Exponent we write native code so other people don't have to.

(I work on Exponent)

When you're developing you can use Exponent's apps from the App Store/Play Store, so you can get started immediately and let other people test your app easily. Once you're ready to put your app in the stores you start a build using our CLI and we build it on our servers (see https://docs.getexponent.com/versions/latest/guides/building...). We want to make it easy for people on Windows and Linux to build apps so don't require you to use Xcode or Android Studio. If you don't want the builds to happen on our servers our clients are open source so you can do it yourself if you want (https://github.com/exponentjs/exponent).

We have some plans to allow custom native modules without forking the client but that's probably a few months out. If you join our slack we'll let you know about any updates: https://slack.exponentjs.com/

If there are any problems, they would probably be easy to fix. The thing I'd be most worried about is just that some things might run very slow on the Pi.

The RPi hardware is pretty slow for a development machine. I have mine minimally overclocked but the CPU temperature was coming close to 85 °C and it took minutes for the starter project to initially load (after that, the build is cached). On the other hand if all you have is a Raspberry Pi, then Exponent is one of the few ways you can make iPhone apps.

Ex. Try opening https://getexponent.com/@exponent/floatyplane from your phone.

If you have the source code for the app, just open the project directory in XDE (our desktop software) and it will give you a development URL that you can open in the Simulator or on your phone.

In general, testing Exponent apps is way easier than testing apps other ways. We put a lot of time into making it simple.

We intentionally chose to not let users drop down to native -- the idea of having an interpreted language that sits on top of a native runtime on multiple platforms is not a new one, and it allows for so many benefits that you lose out on if developers can add arbitrary compiled code with direct access to system APIs.

Additionally, there is a significant value-add of using Exponent in terms of upgrades. As great as React Native is, it also moves extremely fast and it can be difficult to keep up with new releases -- a change in React Native might cause several of your native dependencies to break, and you'll need to fork those libraries and fix them if the maintainer isn't keeping on the same schedule as you. Updates with Exponent are as simple as updating JavaScript, which has much less churn and breaking changes than the native side (the React API itself is very mature, the APIs for specific native components may change).

Another nice advantage of this is that you can work on an iOS app from Windows and Linux, because you don't need to compile your app with Xcode (we handle builds for you when you want to ship to the app store, before that you can just use the Exponent client).

We ship with a bunch of APIs out of the box and are constantly improving them and adding more. We have analytics tools like Amplitude and Segment built in, Maps, Facebook login (working on Google Login), and more: https://docs.getexponent.com/versions/latest/index.html

React Native is still very early, though, and Exponent is just a small team of seven, so we understand that we can't possibly expose every API that developers working with the platform might want. So, we are working on a way for developers to be able to still take advantage of the Exponent toolchain and layer on native code. I've written up our approach in more detail here: https://blog.getexponent.com/answered-on-slack-ejecting-from...

Exponent maintains native modules so they continue to work when React Native changes or when Android & iOS change their APIs. In particular, React Native is released every two weeks and we stay on top of the changelog so you don't have to regarding native modules. We also write native code for both platforms in tandem, often by the same engineer, so that we get coherent APIs that cover common features across both platforms and expose platform-specific capabilities neatly. We want Exponent to feel like a coherent project. All of the docs (and code) for Exponent's modules are in one place, and when you download the Exponent app for development you get all of the native modules right off the bat.

As a data point, the Android version of Li.st (https://play.google.com/store/apps/details?id=st.li.listapp) is built on Exponent and was featured by Google in the Play Store. Li.st is currently one of the best examples of how far you can go with Exponent, and React Native for that matter. We're also on Slack (get an invite here: https://slack.getexponent.com) if you want to chat in real time.

Components aside, you can share your models and data stores, utilities like Immutable.js and lodash, and other environment-agnostic JavaScript. In addition to code, you can share a lot of knowledge like how to write components, structure an app, use npm, and even just write JavaScript.

(2) Exponent is based on React Native which is newer and people seem to like better (search Google for blog posts about experiences using React Native and then search Google for blog posts about using Titanium), though I can't actually compare them personally since I don't know that much about the inner workings of Titanium.

(3) You can do instant app updates with Exponent since the JS is run on the device rather than being cross compiled to native code. I don't think you can do this with Titanium (though I may be wrong -- they've added a lot of features since I last checked on it)

Here are the docs for SDK 10 (based on RN 0.33.0): https://docs.getexponent.com/versions/v10.0.0/index.html

And here are the docs for SDK 9 (based on RN 0.31.0): https://docs.getexponent.com/versions/v9.0.0/index.html

You can use either one.

Also, all our stuff is open source, so just go back and find the old release tags on Github if you want older versions.

Android tablets should work. We don't have native iPad support but we're planning on adding it.