react-inject-env

react-inject-env is a tool that allows you to inject your environment variables after building the static files, allowing you to deploy the same build to multiple environments quickly.

Usage

Sample project

1. Install react-inject-env

npm install react-inject-env --save-dev
yarn add react-inject-env --dev

2. Update Code

• Add the following to index.html

<script src='/env.js'></script>

• Create a new file called env.js and copy the following code:

export const env = { ...process.env, ...window['env'] }

• Replace all instances of process.env with the newly created env variable

import { env } from './env'

export const App = () => {
  return (
    <div style={{backgroundColor: env.REACT_APP_COLOR}}>
      <span>{env.REACT_APP_MAIN_TEXT}</span>
    </div>
  )
}

3. Build your static files

If you are using create-react-app, the command should be npm run build or react-scripts build.

4. Inject environment variables

[env variables] npx react-inject-env set

Pass in all your environment variables.

# with a black background
REACT_APP_COLOR=black REACT_APP_MAIN_TEXT="Black Background" npx react-inject-env set

# with a blue background
REACT_APP_COLOR=blue REACT_APP_MAIN_TEXT="Blue Background" npx react-inject-env set

# for windows
set REACT_APP_COLOR=navy&& set REACT_APP_MAIN_TEXT=Navy Background&& npx react-inject-env set

Additional options

-d / --dir: The location of your static build folder. Defaults to ./build

-n / --name: The name of the env file that is outputted. Defaults to env.js

-v / --var: The variable name in window object that stores the environment variables. The default is env (window.env). However if you already have a variable called window.env, you may rename it to avoid conflicts.

-p / --prefix: Defines the prefix of variables that are supposed to be used. Defaults to REACT_APP_

.env / dotenv

.env files are supported. react-inject-env will automatically detect environment variables in your .env file located in your root folder.

Note: Environment variables passed in through the command line will take precedence over .env variables.

Typescript

In step #2, create a file called env.ts instead of env.js

declare global {
  interface Window {
    env: any
  }
}

// change with your own variables
type EnvType = {
  REACT_APP_COLOR: string,
  REACT_APP_MAIN_TEXT: string,
  REACT_APP_LINK_URL: string,
  REACT_APP_LOGO_URL: string
}
export const env: EnvType = { ...process.env, ...window.env }

Docker / CICD

npx-react-env works well with both Docker and CI/CD.

Sample usage with Docker

FROM node:16.10-slim
COPY . /app
WORKDIR /app

RUN npm install
RUN npm run build

EXPOSE 8080

ENTRYPOINT npx react-inject-env set && npx http-server build

docker build . -t react-inject-env-sample-v2

docker run -p 8080:8080 \                   
-e REACT_APP_COLOR=yellow \
-e REACT_APP_LOGO_URL=./logo512.png \
-e REACT_APP_MAIN_TEXT="docker text" \
-e REACT_APP_LINK_URL=https://docker.link \
react-inject-env-sample-v2

Previous Version v1.0

For instructions on the previous version, you may follow the v1.0 guide here.

Information

Why do I need this?

A typical CI/CD process usually involves building a base image, followed by injecting variables and deploying it.

Unfortunately React applications does not allow for this workflow as it requires environment variables to be present before building it.

There have been a few workarounds, with the most common solution being to load environment variables from an external source. However this now causes the additional problem that environment variables can only be accessed asynchronously.

Goals

react-inject-env attempts to solve this problem in the simplest, and most straightforward way with the following goals in mind:

1. Does not require a rebuild
2. Minimal code change required
3. Allows synchronous access of environment variables
4. Supports a wide amount of tools and scripts
5. Works with command line environment variables
6. Simple and straightforward

Compatibility

react-inject-env was built with support for both create-react-app and dotenv.

However due to the simplicity of it, it should work with almost all scripts and tools.