How to load environment variables in React

Question

I've been trying to load environment variables in React and I can't seem to figure it out. I have tried multiple aproaches:

Load them using the dotenv-webpack package

webpack.config.dev.js

const merge = require('webpack-merge');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const template = require('html-webpack-template');
const Dotenv = require('dotenv-webpack');
const baseConfig = require('./webpack.config.base');

module.exports = merge(baseConfig, {
  mode: 'production',
  plugins: [
    new HtmlWebpackPlugin({
      template,
      inject: false,
      appMountId: 'app',
      mobile: true,
      lang: 'es-ES',
      title: 'My App',
      meta: [
        {
          name: 'description',
          content: 'My App',
        },
      ],
    }),
    new Dotenv(),
  ],
});

.env

API_HOST=http://localhost:8000
REACT_APP_API_HOST=http://localhost:8000

Passing it directly on the package.json script:

"start": "webpack-dev-server --config ./webpack.config.dev.js"

Using .env on the webpack command

webpack --env.API_HOST=http://localhost:8000

Using webpack.environmentPlugin

const webpack = require('webpack');
const merge = require('webpack-merge');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const template = require('html-webpack-template');
const baseConfig = require('./webpack.config.base');

module.exports = merge(baseConfig, {
  mode: 'development',
  devtool: 'cheap-module-source-map',
  devServer: {
    publicPath: '/',
    contentBase: './dist',
    compress: true,
    stats: 'minimal',
    overlay: true,
    historyApiFallback: true,
    port: 8081,
    hot: true,
  },
  plugins: [
    new HtmlWebpackPlugin({
      template,
      devServer: 'http://localhost:8081',
      inject: false,
      appMountId: 'app',
      mobile: true,
      lang: 'es-ES',
      title: 'My App',
      meta: [
        {
          name: 'description',
          content: 'React template.',
        },
      ],
    }),
    new webpack.EnvironmentPlugin({
      API_HOST: 'http://localhost:8000',
    }),
  ],
});

None of this approaches work and when I try to access process.env variables in my React code I get undefined Any ideas of what I could be doing wrong?

Answer 1

I've been fighting with environment variables myself for some time, when I wanted to provide settings to the Firebase project but not load them into the public repository.

As far as I know, you need to name you environment variables should always start with the prefix REACT_APP_. You can define them whereever you like, but if you created your app with create-react-app tool then you can put your variables in .env file, or a few other files - (https://facebook.github.io/create-react-app/docs/adding-custom-environment-variables)

The pain for me started when I wanted to make my own files, because I had two different Firebase projects - one for staging and one for production.

I end up with using react-app-env module which helped with: - defining my own files - staging.env and production.env - auto prefix my variables with REACT_APP_

For example:

I have defined Firebase ApiKey in staging.env file: API_KEY=xxxxxxxxxxxxxxxxxxx

when I use it in my firebase.js file, I use it as:

const config = {
    apiKey: process.env.REACT_APP_API_KEY,
}

And to make sure that I develop against staging environment (Firebase project) I've changed my package.json to:

"scripts": {
    "start": "react-app-env --env-file=staging.env start",
  },

Hope that helps!

Answer 2

You need to specify the webpack config file correct. You will need to create a separate config for dev. (webpack.config.dev.js)

Example here.

scripts: {
    "dev": "webpack --env.API_HOST=http://localhost:8000 --config webpack.config.dev.js"
}

Also, you need to use Webpack.DefinePlugin.

plugins: [
  ...
  new webpack.DefinePlugin({ `process.env.API_HOST`: JSON.stringify(${env.API_HOST}) })
]

or you can use reduce to make it more comprehensive.

  const envKeys = Object.keys(env).reduce((prev, next) => {
    prev[`process.env.${next}`] = JSON.stringify(env[next]);
    return prev;
  }, {});

  return {
    plugins: [
      ...
      new webpack.DefinePlugin(envKeys)
    ]
  };