How to determine if a static variable has been used?
<p>According to the IE Debugger my static variable</p>

<pre><code>link_update.previous_element 
</code></pre>

<p>is set to undefined, the first time through the function.</p>

<p>However when I add in a test for undefined or 'undefined' in parantheses  it does not select it properly as I show in the code below.</p>

<p>How do I detect first use of a static variable?</p>

<pre><code>function link_update( link_display )
{
    current_element = document.getElementById( link_display )
    current_element.style.opacity = 1;
    if( link_update.previous_element != undefined)
    {
        link_update.previous_element.style.opacity = 0;
    }
    link_update.previous_element = current_element;
}
</code></pre>
