Problem with comparing tagName in IF statement

I have a Javascript function that is highlighting the menu in one of my courses. I am having a problem getting into an If statement in some cases. Here is my code:
function hilightCurrent() {
var nav = document.getElementById('nav');
if (nav == null) {
return;
}

var checkIndex = hreftable[__currpage];
var aObj = nav.getElementsByTagName('a');
var found = false;

while ((found == false) && (checkIndex > -1)){
for(j=0; j < aObj.length; j++) {
if(aObj[j].href.indexOf(index[checkIndex].href)>=0) {
aObj[j].className='active';
alert("parent tag = " + aObj[j].parentNode.parentNode.parentNode.tagName);
if(aObj[j].parentNode.parentNode.parentNode.getElementsByTagName == 'li'){
aObj[j].parentNode.parentNode.parentNode.className='active';
aObj[j].parentNode.parentNode.parentNode.getElementsByTagName('a')[0].className='active';
}
found = true;
break;
}
}
checkIndex--;
}
}

The alert I have in there currently is returning LI in the case where I want to get into the IF statement right below it. So the alert comes back as LI and then I am checking if it is LI but for some reason it doesn't get into that if statement. Can anyone help or have any ideas?

Thanks!

tagName values are uppercase.

Thanks for the reply. I have tried changing it to:

if(aObj[j].parentNode.parentNode.parentNode.getElementsByTagName == 'LI'){
aObj[j].parentNode.parentNode.parentNode.className='active';
aObj[j].parentNode.parentNode.parentNode.getElementsByTagName('a')[0].className='active';
}

Unfortunately it still is not getting inside the IF. Any other ideas?

Thanks!

Oops, I pasted the wrong code in my last post. I mean I tried changing to this:

if(aObj[j].parentNode.parentNode.parentNode.tagName == 'LI'){
aObj[j].parentNode.parentNode.parentNode.className='active';
aObj[j].parentNode.parentNode.parentNode.getElementsByTagName('a')[0].className='active';
}