title: what's correct: var declaration if undefined
body: <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 not, because <code>maybeUndefined</code> is an <code>argument</code> of <code>function</code>?</p>