Easiest way to get file ID from URL on Google Apps Script

Question

Here is what I'm trying to do: given a Google document URL, I want to get the document ID to create a copy on Google Drive. I know I can achieve that by some regex or replacing on the URL, but as there are several different forms to represent the same document in a URL, I wanted to find a generic solution.

Currently, that's the best I could think:

function getFileIdFromUrl(url) {
  try {
    return getDocIdFromUrl(url);
  } catch (e) {
    return getSpreadsheetIdFromUrl(url);
  }
}

function getDocIdFromUrl(url) {
  var doc = null;
  try {
    doc = DocumentApp.openByUrl(url);
  } catch (e) {
    doc = DocumentApp.openByUrl(url + "/edit");
  }
  return doc.getId();
}

function getSpreadsheetIdFromUrl(url) {
  var spreadsheet = null;
  try {
    spreadsheet = SpreadsheetApp.openByUrl(url);
  } catch (e) {
    spreadsheet = SpreadsheetApp.openByUrl(url + "/edit");
  }
  return spreadsheet.getId();
}

function copy(url) { // may throw an exception if the URL is invalid or private
   var id = getFileIdFromUrl(url);
   var file = DriveApp.getFileById(id);
   file.makeCopy().setSharing(DriveApp.Access.ANYONE_WITH_LINK, DriveApp.Permission.VIEW);
}

The problem is that my solution only covers documents and spreadsheets, I would like to do the same with any uploaded file, for example:

https://docs.google.com/file/d/0B-FYu_D7D7x4REdtRVEzVH0eU0/edit

In short, I wanted something like that:

DriveApp.getFileByUrl(url).makeCopy();

Does anyone know if it's possible?

Any safe solution to extract the file ID from the file URL would fit as well for me.

Thanks

Answer 1

DriveApp is indeed missing a getFileByUrl (and also folder for that matter). You may want to open an enhancement request on Apps Script issue tracker.

But what I do on my scripts (since these openByUrl functions are somewhat new), is to get the id using a regex. Like this.

function getIdFromUrl(url) { return url.match(/[-\w]{25,}/); }

This regex works for any google url I've tried: Drive url for folders and files, Fusion Tables, Spreadsheets, Docs, Presentations, etc. It just looks for anything in a string that "looks like" a Google key. That is, any big enough string that has only (google key) valid characters in it.

Also, it works even if it receives the ID directly, instead of the URL. Which is useful when you're asking the link from the user, as some may paste the id directly instead of the url and it still works.

--edit

There are some other answers and comments that address some edge cases that I never encountered myself but might happen, like trying to get a folder-id on a nested folder URL, or when you have G-Suite domain that is 25+ characters long. For those cases, you might want to use a more strict regex.

From a quick look at the suggestions below I recommend the following /[-\w]{25,}$/ because it is still very simple and should address these cases.