How to get the folder of the recent document - google-apps-script

Question

I run a script inside a google document. How can I get the recent folder where this document is in, or how do I create a subfolder of the recent folder of my document?
I want to create a subfolder but this subfolder always is created on the top level in google drive.
`if (!DriveApp.getFoldersByName("myNewFolder")) DriveApp.createFolder("myNewFolder");`
So it seems that the active folder is the toplevel folder.
There is no DocumentApp.getMyFolder() or DriveApp.getRecentFolder() method.
Is there maybe some kind of LINUX-style pre-thing like
DriveApp.createFolder("./myNewFolder");
So how do I get the recent folder, or - even better - How do I create a new folder in the recent folder and then create a new document inside this new folder? Remark: The folder should only be created new if it does not already exist.
Thanks a lot!

Answer 1

Problem
Create a folder in a folder in Goolge Drive (directly, without moving) where a Google Document is stored.
Solution
This sample utility function gets the parent Folder of a file by its Id:
/**
* Gets file location;
* #param {String} id document id;
* #return {Folder|null} file's folder;
*/
function getLocation(id) {
var file = DriveApp.getFileById(id);
var folders = file.getParents();
if(folders.hasNext()) {
return folders.next();
}else {
return null;
}
}
Get the parent folder of the current document (assuming your script is bound to the document, otherwise procure the Id by other means):
function createSubfolderInCurr() {
var id = DocumentApp.getActiveDocument().getId();
var folder = getLocation(id);
if(folder) {
//part 3 goes here;
}
}
Check if a subfolder already exists and create one if needed:
var exists = folder.getFoldersByName('myNewFolder').hasNext();
if(!exists) {
var newfolder = folder.createFolder('myNewFolder');
//part 4 goes here;
}
As for creating a new document in that folder, first you need to create a Document, then access it as a File and move from root to the newly created folder:
var newdoc = DocumentApp.create('NewFile');
var newId = newdoc.getId();
var newfile = DriveApp.getFileById(newId);
DriveApp.removeFile(newfile);
newfolder.addFile(newfile);
Reference
getParents() method reference;
getFoldersByName() method reference ('Folder' class);
createFolder() method reference (Folder class);
create() method reference (DocumentApp class);
removeFile() method reference (DriveApp class);
addFile() method reference (Folder class);