title: How to make Flow understand code written for Node.js?
body: <p>I'm just getting started with Flow, trying to introduce it into an existing Node codebase.</p>
  
  <p>Here are two lines Flow complains about:</p>
  
  <pre><code>import Module from 'module';
  
  const nodeVersion = Number(process.versions.node.split('.')[0]);
  </code></pre>
  
  <p>The warnings about these lines are, respectively:</p>
  
  <pre><code>module. Required module not found
  
  call of method `split`. Method cannot be called on possibly null value
  </code></pre>
  
  <p>So it seems like Flow isn't aware of some things that are standard in a Node environment (e.g. <code>process.versions.node</code> is guaranteed to be a string, and there is <em>definitely</em> a Node builtin called <code>module</code>).</p>
  
  <p>But then again, Flow's <a href="https://flowtype.org/docs/advanced-configuration.html" rel="nofollow">configuration docs</a> suggest it's Node-aware by default. And I have plenty of other stuff like <code>import fs from 'fs';</code> which does <strong>not</strong> cause any warning. So what am I doing wrong?</p>