This is a sample script for creating a folder tree including all folders in Google Drive. For each element, parent folder and sub folder are retrieved.
Script :
var results = (function(folder, folderSt, results){
var ar = [];
var folders = folder.getFolders();
while(folders.hasNext()) ar.push(folders.next());
folderSt += folder.getName() + "(" + folder.getId() + ")#_aabbccddee_#";
var array_folderSt = folderSt.split("#_aabbccddee_#");
array_folderSt.pop()
results.push(array_folderSt);
ar.length == 0 && (folderSt = "");
for (var i in ar) arguments.callee(ar[i], folderSt, results);
return results;
})(DriveApp.getRootFolder(),"",[]);
Result :
[
[foldername1(folder1 id)],
[foldername1(folder1 id), sub foldername1s(sub folde1s id)],
[foldername1(folder2 id)],
[foldername2(folder2 id), sub foldername2s1(sub folde2s1 id)],
[foldername2(folder2 id), sub foldername2s1(sub folde2s1 id), sub foldername2s2(sub folde2s2 id)]
]
By the way :
ar.length == 0 && (folderSt = "");
if (ar.length == 0) {
folderSt = "";
}
Both scripts are the same meaning.