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Snack is the easiest way to experiment and explore working React Native code. It is the first stop for anyone curious what RN is all about, and a constant companion for experienced developers to experiment, collaborate and learn.
With Snack, it’s possible to prototype a React Native app on its web based editor and instantly preview it on the device with the Expo app or the web based simulator.
Snack is one of the many projects from Expo, aimed to make working with React Native and Expo easier.
This poses a great barrier to people who want to try out React Native. With Snack, we wanted to make this easier by addressing following groups of people and their use cases:
Starting a React Native project is a lot of work, including setting up the developer environment and various tools. In addition, projects which were working few days earlier could stop working without any changes if not using something like a yarn.lock or package-lock.json.
We needed to build something that requires no setup, can be previewed instantly on real devices and easily shared with others. We faced several challenges:
We also needed to build a web based editor which provides a good editing experience with linting, managing multiple files with drag and drop, logging etc.
The first problem we needed to solve was to minimize the setup required. Fortunately, the expo development environment already takes care of this. While using Expo would solve this issue, it still took a little bit of work. Another approach was to run a React Native development environment on the cloud (rnplay.org) RNPlay. However it was really slow and unusable. To avoid running metro-bundler, we decided to patch in the code that has changed instead of rebuilding the full bundle every time. For the web based editor, we decided to use Ace Editor with a custom ESLint build for linting the files.
Our final approach involved a web based editor with a companion app running inside the Expo app on the device which patches in the changed code. The Expo app can load the experience by opening a link to the snack or by scanning a QR code.
The basic approach is that the web UI sends the code and the list of dependencies to the app, the app downloads the dependencies, transforms the code with Babel, and then executes it. Source
We used Ace Editor for the code editor with various enhancements to improve the editing experience, such as ESLint and Prettier integration, various keyboard shortcut, file management support etc.: source
We also built a custom packager which creates bundles to be used by projects on Snack, so you could import a module like usual and we take care of the rest behind the scenes. The packager is based on webpack with custom loaders and plugins: source
We managed to achieve the goals we originally set and constantly iterating on improving the experience and adding new features.
We’re happy to be able to help the community by lowering the barriers to entry and experimentation with Snack and excited to see what new ideas the community comes up with. If you are using React Native and haven’t checked it out yet, you definitely should!
Need help with React or React Native? Let us know!