Behavior of delete operator in javascript
<p>It seems in JavaScript you can’t <code>delete</code> function arguments but you 
can <code>delete</code> global variables from a function.</p>

<p>Why this behavior?</p>

<pre><code>var y = 1;
(function (x) { return delete y; })(1); // true

(function (x) { return delete x; })(1); // false
</code></pre>
