what's correct: var declaration if undefined
<p>I have heard different opinions about the usage of <code>var</code> at a situation like this:</p>

<pre><code>function(mayBeUndefined){
    if(typeof mayBeUndefined === 'undefined')
        var mayBeUndefined = 'bob';
}
</code></pre>

<p>Is it necessary to notate <code>var</code>, or is <code>mayBeUndefined</code> already a local variable because it is an <code>argument</code> of <code>function</code>?</p>
