Determining the depth of a nested HTML list

I had this problem the other day that I needed to know how many nesting levels a menu has. After some failed attempts of walking the DOM and lots of comparisons I realised that it is actually a lot easier than I thought:

function treedepth(o){

var nested = o.getElementsByTagName(‘ul’);

var allcount = 0;

for(var i=0,j=nested.length;i<;i++){

var count = 1;

var kid = nested[i].getElementsByTagName(‘ul’)[0];

while(kid!==undefined){

count++;

kid = kid.getElementsByTagName(‘ul’)[0];

}

	
if(count>allcount){allcount=count;}

}
	
return allcount;

}

You can check a testcase for treedepth here.

Any better way to do this?