请教一段jsp上js代码,请高手明示.

Question

var Fac = new dTree('Fac', '/pragmatic-internals/img/tree',false);
Fac.add(0,1,'A','javascript:selectItem(0,0,1);','','','','',false,0);.........
请问下面是什么意识,点击一个树节点是,是怎么处理的;
var maxLength=Fac.aNodes.length;
<%if(paperID!=null&&!paperID.equals("")&&!paperID.equals("0")){%>
var indexId = 0;
var paperID="<%=paperID%>";for(;indexId<maxLength;indexId++){
if(Fac.aNodes[indexId].id==paperID)break;
}
if(indexId==maxLength){
indexId=0; 
}
var parentId=Fac.aNodes[indexId].pid
eval('document.all.sFac'+indexId+'.className = "nodeSel"');
eval('Fac.selectedNode='+indexId);
var idString=paperID+"g";
if(idString.indexOf("T")!=-1) {
paperID = paperID.substring(1);
}if(parentId==0){
parent.selectItem(paperID,1,0);
}else{
parent.selectItem(paperID,2,0);
}
<%}else{%>var child=0;
for(;child<maxLength;child++){
if(Fac.aNodes[child].pid==0)break;
}if(child<maxLength){
parent.selectItem(0,0,1);
}else{
parent.selectItem(0,0,1);
}
Fac.selectedNode=0;
document.all.sFac0.className = "nodeSel";
//parent.document.getElementById("newButton").disabled=false;
//parent.theLevel=0;
<%}%>
function selectItem(id,level,hasChild){
//    parent.goToEdit(id);
parent.selectItem(id,level,hasChild);

}
function selectItem(id,level,name,hasChild){
//    parent.goToEdit(id);
parent.selectItem(id,level,hasChild);

}
function selectX(node){alert(aNodes[node].url);
}