Javascript object literals don't allow references to existing values?
<p>I have an object, defined thus:</p>

<pre><code>var obj = {
    'title': 'foo',
    'id': '123',
    'category': 'aaa',
    'meta': 'blah blah'
};
</code></pre>

<p>I'd like to subset it, however, I discovered some behavior in JS which I don't understand:</p>

<pre><code>var foo = {obj.title: obj.id}; // doesn't work
var bar = {obj['title']: obj['id']}; // this doesn't either

var baz = {}
baz[obj.title] = obj.id // this works fine.
</code></pre>

<h1>Why?</h1>
