frontend/config/env.js

const fs = require("fs")
const path = require("path")
const paths = require("./paths")

// Make sure that including paths.js after env.js will read .env variables.
delete require.cache[require.resolve("./paths")]

const NODE_ENV = process.env.NODE_ENV
if (!NODE_ENV) {
  throw new Error("The NODE_ENV environment variable is required but was not specified.")
}

// https://github.com/bkeepers/dotenv#what-other-env-files-can-i-use
const dotenvFiles = [
  `${paths.dotenv}.${NODE_ENV}.local`,
  // Don't include `.env.local` for `test` environment
  // since normally you expect tests to produce the same
  // results for everyone
  NODE_ENV !== "test" && `${paths.dotenv}.local`,
  `${paths.dotenv}.${NODE_ENV}`,
  paths.dotenv
].filter(Boolean)

// Load environment variables from .env* files. Suppress warnings using silent
// if this file is missing. dotenv will never modify any environment variables
// that have already been set.  Variable expansion is supported in .env files.
// https://github.com/motdotla/dotenv
// https://github.com/motdotla/dotenv-expand
dotenvFiles.forEach((dotenvFile) => {
  if (fs.existsSync(dotenvFile)) {
    require("dotenv-expand")(
      require("dotenv").config({
        path: dotenvFile
      })
    )
  }
})

// We support resolving modules according to `NODE_PATH`.
// This lets you use absolute paths in imports inside large monorepos:
// https://github.com/facebook/create-react-app/issues/253.
// It works similar to `NODE_PATH` in Node itself:
// https://nodejs.org/api/modules.html#modules_loading_from_the_global_folders
// Note that unlike in Node, only *relative* paths from `NODE_PATH` are honored.
// Otherwise, we risk importing Node.js core modules into an app instead of webpack shims.
// https://github.com/facebook/create-react-app/issues/1023#issuecomment-265344421
// We also resolve them to make sure all tools using them work consistently.
const appDirectory = fs.realpathSync(process.cwd())
process.env.NODE_PATH = (process.env.NODE_PATH || "")
  .split(path.delimiter)
  .filter((folder) => folder && !path.isAbsolute(folder))
  .map((folder) => path.resolve(appDirectory, folder))
  .join(path.delimiter)

// Grab NODE_ENV and REACT_APP_* environment variables and prepare them to be
// injected into the application via DefinePlugin in webpack configuration.
const REACT_APP = /^REACT_APP_/i

function getClientEnvironment(publicUrl) {
  const raw = Object.keys(process.env)
    .filter((key) => REACT_APP.test(key))
    .reduce(
      (env, key) => {
        env[key] = process.env[key]
        return env
      },
      {
        // Useful for determining whether we’re running in production mode.
        // Most importantly, it switches React into the correct mode.
        NODE_ENV: process.env.NODE_ENV || "development",
        // Useful for resolving the correct path to static assets in `public`.
        // For example, <img src={process.env.PUBLIC_URL + '/img/logo.png'} />.
        // This should only be used as an escape hatch. Normally you would put
        // images into the `src` and `import` them in code to get their paths.
        PUBLIC_URL: publicUrl,
        // We support configuring the sockjs pathname during development.
        // These settings let a developer run multiple simultaneous projects.
        // They are used as the connection `hostname`, `pathname` and `port`
        // in webpackHotDevClient. They are used as the `sockHost`, `sockPath`
        // and `sockPort` options in webpack-dev-server.
        WDS_SOCKET_HOST: process.env.WDS_SOCKET_HOST,
        WDS_SOCKET_PATH: process.env.WDS_SOCKET_PATH,
        WDS_SOCKET_PORT: process.env.WDS_SOCKET_PORT,
        // Whether or not react-refresh is enabled.
        // react-refresh is not 100% stable at this time,
        // which is why it's disabled by default.
        // It is defined here so it is available in the webpackHotDevClient.
        BASE_URL: process.env.BASE_URL,
        UNIFIED_API: process.env.UNIFIED_API,
        UNIFIED_URL: process.env.UNIFIED_URL
      }
    )
  // Stringify all values so we can feed into webpack DefinePlugin
  const stringified = {
    "process.env": Object.keys(raw).reduce((env, key) => {
      env[key] = JSON.stringify(raw[key])
      return env
    }, {})
  }

  return { raw, stringified }
}

module.exports = getClientEnvironment