Simple javascript function - if statement not triggering?

I have an overly simple javascript function and I can't figure out why the if statement isn't triggering in it:

var theChange;
function showChangeBox(theChange) {
    if (theChange == 'fName') {
        document.getElementById('userPanelChangeBox').innerHTML = 'Some HTML';
        }
    document.getElementById('userPanelChangeBox').style.display = "block";
    return;
    }

It's called by an onClick:

<a href="#" onclick="showChangeBox('fname');">Click to Change</a>

Simple, right? I've done a bunch of these before, I can't figure out why this isn't working, I'm sure it's something ridiculous that I missed but after staring at it for 20 minutes, my tunnel vision might be preventing me from seeing the error.

It's开发者_如何学JAVA triggering the change to the display, but I know it isn't going to the if because if I put an alert in it, I get no alert. Grrr. Thanks for the help.

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It's a matter of case, "fName" != "fname".