How to modify ajax response before jsTree creation?

How can I modify ajax response before jsTree creation? I would like to access each node ID and add prefix to it. On jsTree page the only clue is this: the function will receive two arguments - the node being loaded & a function". I need to do that before the tree is actually created, to avoid duplicate ID in the document.

"json_data" : {
"ajax" : { 
  "type": "GET", 
  "url" : "tree.json" 
 }, 
"d开发者_开发百科ata" : function(node, func){
        //how to use that? 
}} 

I have expected to get JSON data here, modify it and return? But this will explode.

I have successfully manipulated data using the success callback in the instantiation of the jsTree. In my case, I am parsing XML data returned as JSON from a .NET webmethod. It should work for your case in a similar manner.

"ajax": {
  "type": "GET"
  "url": "tree.json",
  "success": function (x) {
    //manipulate string x to change id's here
    return x;
  }, ...

Another method is to use the "complete" callback function to manipulate the jsTree in its final form. I don't recommend it in your case of duplicate id's, however.