Test Value of Retrieved Cookie

I feel foolish posting this question, but I'm completely baffled. I'm simply trying to retrieve a cookie, check its value and do something.

<script type="text/javascript" language="JavaScript">
var loggedIn
function checkLogin()
{
	alert("Get Cookie");
	loggedIn=getCookie("login");
	alert(loggedIn);
	If ((loggedIn == null) || (loggedIn == "NO"))
	{
	alert("Not logged In");
	}
}

function getCookie(name) 
{
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') c = c.substring(1,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
}
</script>
<div id="addEvent">
          <input name="addEvent" type="button" value="Add an Event" onclick="checkLogin()" />
        </div>

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I've tested with values of null and NO. Both alerts execute, returning values of "null" and "NO" -  and then nothing.