title: Firebase client on ReactNative
body: <p>When using Firebase on ReactNative, it will show such error message:</p>
  
  <blockquote>
    <p>can't find variable process</p>
  </blockquote>
  
  <p>However, if I require <code>firebase/lib/firebase-web.js</code> manually, it will show:</p>
  
  <blockquote>
    <p>can't find variable document</p>
  </blockquote>
  
  <p>How can I resolve this?</p>