Argument placeholder
<p>The following piece of code from the jQuery source caught my eye (line 7716 from the latest revision bit.ly/jqsource):</p>

<pre><code>        send: function( _, callback ) {

            script = document.createElement( "script" );

            script.async = "async";

// BLA BLA BLA
        }
</code></pre>

<p>At no point is the named parameter <code>_</code> used. It seems this is to force <code>callback</code> to be <code>arguments[1]</code> instead of <code>arguments[0]</code>. Why would that be useful?</p>
