What does crockford mean when he says that undefined cannot be a property value?
<p>In the book Javascript the good parts, on the opening page of Ch3 on objects, it states:</p>

<blockquote>
  <p>An object is a container of properties, where a property has a name and a value. A property name can be any string, including the empty string. A property value can be any Javascript value except for undefined.</p>
</blockquote>

<p><em>Note</em>: <em>undefined</em> is highlighted in the book to denote that is is a literal.</p>

<p>In practice, however, I am able to do it.</p>

<pre><code>var a = { "name": undefined };
</code></pre>

<p>What is wrong with my understanding ?</p>
