在 FolderIterator 和 FileIterator 上循环 - Google Apps 脚本

Question

I'm making a script to loop in a Google Drive folder and noticed I don't know what's the best way to loop over iterators (specifically FolderIterator and FileIterator). My first approach

const drive_id  = '__________';
let base_folder = DriveApp.getFolderById(drive_id),
    sub_folders = base_folder.getFolders();
Logger.log(base_folder.getFolders());
for(let sub_folder of sub_folders) 
{
    Logger.log(sub_folder);
}

outputs Error TypeError: sub_folders is not iterable .

Secondly I tried with while loops and checks on hasNext(), but I didn't find them beautifyl enough. I'm currently set with this for loop, that works and is clean enough but still looks a bit hacky.

/*...*/
for(let sub_folders = base_folder.getFolders(); sub_folders.hasNext();)
{
  let sub_folder = sub_folders.next();
  Logger.log(sub_folder);
}

Also notice how I couldn't declare sub_folder within the loop itself. So, what's the proper way of doing it?

Also, what if I wanted to use a map or filter on the sub_folders instead?

Note: this question is probably of broader scope than google-script, but I couldn't find the right terminology to ask the question differently so I preferred to stick to the particular case I found.

Answer 1

What's the proper way of looping a FolderIterator or FileIterator?

• The proper way of doing it by using a while loop.

• The reason for that has to do with the hasNext() function which returns a Boolean ( true or false ) and the only loop that natively works with booleans is the while loop.

Also, what if I wanted to use a map or filter on the sub_folders instead?

• In your code sub_folder is an object of type Folder . Unfortunately, you can only retrieve the folders one by one within the while loop by using next() so you can't directly apply map or filter on the FolderIterator .

• Instead, you can create an array of folders by pushing each folder to an array (within the while loop) and then use map .

Example:

This script finds all the folders and store them in an array and then uses map to get the name of each sub folder:

function myFunction() {
  const base_folder  = DriveApp.getFolderById('folder_id');
  const sub_folders  = base_folder.getFolders();
  const folders = [];

  while (sub_folders.hasNext()){
    let folder = sub_folders.next()
    folders.push(folder);
  }
  
  const folder_names = folders.map(f=>f.getName());
  console.log(folder_names);
} 

Here is a list of all the available methods you can apply to each element of the folders array: Class Folder