How can I check if the value of a parameter passed to a javascript function is null?
<p>I have the following javascript code:</p>

<pre><code>    function changeButtonState(targetSelector, action, iconClass) {
        var $target = $(targetSelector);
        var $targetSpan = $(targetSelector + ' span');
        $targetSpan.removeClass('sprite-blank').addClass(iconClass);
</code></pre>

<p>How can I make it so that the <code>$targetSpan.removeClass(..).addClass</code> only work if the iconClass has a 
value when the function is called. I guess what I am confused about is do I check if it is defined
or do I check if it has a length of 0 or more?</p>
