title: When use npm cache and why?
body: <p>When do I have to use <code>npm cache clean</code>  ? 
  And, why after using <code>npm cache clean</code> do I get  <code>info trying</code> ?</p>
  
  <pre><code>info trying registry request attempt 1 at 09:54:07
  
  http GET https://registry.npmjs.org/delayed-stream/latest
  http 304 https://registry.npmjs.org/delayed-stream/latest
  </code></pre>