title: .env variable returns undefined in React JS app
body: <p>I am working on this react app and thinking of adding some environment variables inside, this is what I've done:</p>
  
  <ol>
  <li>installed the latest version of react-scripts</li>
  <li>added .env file on the root folder (the same location where node_modules folder is)</li>
  <li>added REACT_APP_OTHER_OTHER_THING=asdfas just to test the variable</li>
  </ol>
  
  <blockquote>
  <pre><code>REACT_APP_OTHER_OTHER_THING=asdfas
  </code></pre>
  </blockquote>
  
  <ol start="4">
  <li>open index.js and console.log(process.env.REACT_APP_OTHER_OTHER_THING) inside to see the output</li>
  </ol>
  
  <blockquote>
  <pre><code>import React from 'react';
  import Reactdom from 'react-dom';
  import App from './App';
  
  console.log(process.env.REACT_APP_OTHER_OTHER_THING, 'DOTENV')
  
  Reactdom.render(&lt;App/&gt;, document.getElementById("app"))
  </code></pre>
  </blockquote>
  
  <p>then I rebuilt the app and started the app to see the result
  but then it gives out undefined as the output for process.env.REACT_APP_OTHER_OTHER_THING. I then tried to print process.env.NODE_ENV (which is working and prints "development" as output).</p>
  
  <p>note: I have also tried to add temporary variable as the docs said in <a href="https://create-react-app.dev/docs/adding-custom-environment-variables" rel="noreferrer">https://create-react-app.dev/docs/adding-custom-environment-variables</a> >> rebuilt the server and run <strong><em>($env:REACT_APP_OTHER_OTHER_THING= "abcdef") -and (npm start)</em></strong> &lt;&lt; due to me running it on powershell which still gives undefined as output.</p>
  
  <p>is there anything I can do on this?
  thank you</p>