title: What is the "-d" in "npm -d install"?
body: <p>I've seen some posts that refer to running <code>npm</code> with a <code>-d</code> argument. For example, <a href="https://github.com/visionmedia/mocha/pull/73" rel="noreferrer">this issue</a> refers to doing <code>npm -d install coffee-script</code>. There are <a href="https://www.google.com/search?q=%22npm%20-d%20install%22" rel="noreferrer">a few other pages</a> that also refer to this syntax, including the <a href="https://github.com/hbons/SparkleShare-Dashboard/wiki" rel="noreferrer">install instructions</a> for at least one npm package.</p>
  
  <p>But I've been unable to find any documentation for this <code>-d</code> argument. The <a href="http://npmjs.org/doc/install.html" rel="noreferrer">docs for <code>npm install</code></a> make no mention of <code>-d</code>, nor does <a href="http://npmjs.org/doc/faq.html" rel="noreferrer">the npm FAQ</a>, nor do any of the other documentation pages I've looked through.</p>
  
  <p>Does the <code>-d</code> option do anything? If so, what?</p>