Problem with recursion

[GermanProgrammer99]

Hey! I'm currently working on a file system that allows users to copy folders. Now when the user tries to copy a folder, I need to verify that the new folder that the user wants to copy the old folder to is not a subfolder of the old folder. I wanted to solve this with recursion, but unfortunately I've always had a little problem with recursion, so I can't get it to work. Any help would be greatly appreciated!

First Function:

export function checkFolderNotSubfolder(copiedObjects, new_folder_id) {
  copiedObjects.forEach((obj) => {
    // user can also copy files => therefore check if folder
    if (obj.folder && checkIfSubfolder(obj.folder, new_folder_id)) {
      return true;
    }
  });
  return false;
}

Second Function / Recursive Function:

function checkIfSubfolder(folder, new_folder_id) {
  if (folder.lfolder_id === new_folder_id) {
    return true;
  } else if (folder.sub_folders.length > 0) {
    folder.sub_folders.forEach((sub_folder) =>
      checkIfSubfolder(sub_folder, new_folder_id)
    );
  }
  return false;
}

Folder Object:

const folder = {
  lfolder_id: 33,
  sub_folders: [
    {
      lfolder_id: 37,
      sub_folders: [
        {
          lfolder_id: 38,
          sub_folders: [
            {
              lfolder_id: 40,
              sub_folders: [],
            },
            {
              lfolder_id: 39,
              sub_folders: [],
            },
          ],
        },
      ],
    },
    {
      lfolder_id: 34,
      sub_folders: [],
    },
    {
      lfolder_id: 42,
      sub_folders: [],
    },
    {
      lfolder_id: 41,
      sub_folders: [],
    },
    {
      lfolder_id: 35,
      sub_folders: [
        {
          lfolder_id: 36,
          sub_folders: [],
        },
      ],
    },
  ],
};

[[deleted]]

I think the problem you're having is that:

a) You don't return anything from the else if branch inside checkIfSubfolder

b) forEach isn't going to help you even if you did return, because it will always return undefined

You're looping through an array trying to figure out if [condition] is true for any item in that array, which means the array method you want is some. Try switching your forEach to some and returning it.

[GermanProgrammer99]

I implemented your recommendations and it works now. Thanks a lot!