expo-config

expo-config is a port of the popular Node-Config package to the Expo Framework. This allows you to create multiple config files, and choosing which to use based on things like environment variables. We are able to do this by taking advantage of Expos Constants API and the app.json file.

Installation

simply run the command

npm install --save expo-config

Setup

To setup the config files, please follow the guidelines of the Node-Config package for folder structure and config file naming convention.

A quick example might look like at the root of your project:

project
│   App.js
│   package.json   
│
└───config
│   │   default.json
│   │   development.json
│   │   development-local.json
│   │   production.json
│   │   ...
│   │
│   
└───src
    │   ...
    │ 

A sample config file might look something like:

{
  "facebookAppID": "XXXXXX",
  "apiUrl": "http://example.com"
}

expo-config comes with a cli tool to help streamline everything for you. Here is what your scripts in your package.json might look like now:

{
  "scripts": {
    "config:dev-local": "NODE_ENV=development NODE_APP_INSTANCE=local expo-config",
    "config:production": "NODE_ENV=production expo-config",
    "dev": "npm run config:dev-local && expo start",
    "build:android": "npm run config:production && expo build:android"
    ... other scripts
  }
}

Usage

Once you have the package setup in your project, to use the config is quite simple. An example of using the config is as follows:

import config from 'expo-config'
 
console.log(config.facebookAppID)

Notes

One thing I've noticed is that Expo caches the app.json file pretty good. So if you make a change to the config file, or want to stop the expo server and start up with a new config file, it may require a restart of the simulator to get the new config options.

If anyone has suggestions on improvements, please feel free to create an issue or make a merge request!

Thank You!