Something like jQuery.extend() but standalone?
<p>I'm looking for a way to merge two configuration objects together, something like:</p>

<pre><code>var developmentConfig = {
  url: "localhost",
  port: 80
};

var productionConfig = {
  url: "example.com"
};

var config = isDevelopment ? developmentConfig : jQuery.extend(developmentConfig, productionConfig);
</code></pre>

<p>However, this is a Node.js app and I don't want to include jQuery and am looking for something similar but standalone. I know I could write something similar myself but I'd rather use something tested and proven (there are edge cases, complications when the config objects use richer hierarchies etc.)</p>

<p><strong>Edit</strong>: Simple iteration is not enough because that does not handle hierarchical structures. Neither does Underscore's <code>extend</code>.</p>
