Setting environment variable in react-native?

Question

I am using react-native to build a cross-platform app, but I do not know how to set the environment variable so that I can have different constants for different environments.

Example:

development: 
  BASE_URL: '',
  API_KEY: '',
staging: 
  BASE_URL: '',
  API_KEY: '',
production:
  BASE_URL: '',
  API_KEY: '',

Answer 1

Instead of hard-coding your app constants and doing a switch on the environment (I'll explain how to do that in a moment), I suggest using the twelve factor suggestion of having your build process define your BASE_URL and your API_KEY.

To answer how to expose your environment to react-native, I suggest using Babel's babel-plugin-transform-inline-environment-variables.

To get this working you need to download the plugin and then you will need to setup a .babelrc and it should look something like this:

{
  "presets": ["react-native"],
  "plugins": [
    "transform-inline-environment-variables"
  ]
}

And so if you transpile your react-native code by running API_KEY=my-app-id react-native bundle (or start, run-ios, or run-android) then all you have to do is have your code look like this:

const apiKey = process.env['API_KEY'];

And then Babel will replace that with:

const apiKey = 'my-app-id';

Hope this helps!