I try to get the level of a selected node in a treeview using (client-side) javascript:

function ChangeSection(section)
{
if (section== 2)
{
var link = document.getElementById("tvPaysProvVille");
var node = link.selectedNodes;
var selNodeLevel = node.level;
if (selNodeLevel == 0)
{
document.form1.elements["hfTreeViewObject"].value="le pays";
alert(document.form1.elements["hfTreeViewObject"].value);
}
else
...
return;
}
}

but the system reports: node, as having an undefinite value and does not recognize: selNodeLevel as a valid object; What code should be used to get the desired result?