Can't find modules required in React : <p>I was going through the React codebase, and I noticed how React's <code>require</code> doesn't quite behave like in Nodejs. I don't get what's going on here.</p>

<p>Looking at line 19 on ReactClass.js for instance, there's a <code>require('emptyObject')</code>, but emptyObject isn't listed in package.json, nor does it say anywhere where that module's coming from.</p>

<p><a href="https://github.com/facebook/react/blob/master/src/isomorphic/classic/class/ReactClass.js#L19" rel="nofollow">https://github.com/facebook/react/blob/master/src/isomorphic/classic/class/ReactClass.js#L19</a></p>

<p>I did find <a href="https://www.npmjs.com/package/emptyObject" rel="nofollow">"emptyObject" on npmjs</a>, but the API there seems different from the one used in React; the <code>.isEmpty</code> grepped in React isn't related to emptyObject.</p>

<p>So where is emptyObject getting loaded from, and how is React's <code>require</code> doing what it's doing? This is not intuitive. At all.</p>
