Remove "Copy of" filename prefix when copying an entire folder from one Google Drive account to another Google Drive account

Drive rename.js

/* Need to copy an entire folder from one Google Drive account to another Google Drive account? 
 * 1. Right-click on original folder in Google Drive
 * 2. Share with the destination Google account
 * 3. Go into destination account's Google Drive
 * 4. Find the shared folder under "Shared with me"
 * 5. Select all the files (Ctrl-A / Cmd-A)
 * 6. Right-click, Make a copy
 * 7. Create a New Folder in destination account's Google Drive
 * 8. Go to Recent
 * 9. Select all recently copied files and move to the new folder
 * 10. Great, except all the filenames begin with "Copy of"xxxxxx.txt
 * 11. Create a new Apps Script, perhaps using Google Sheets, and use the below script to remove the "Copy of" filename prefix!
 */

function fileRename() {
  var folders = DriveApp.getFoldersByName('FOLDERNAME');
  var folder = folders.next();
  var files = folder.getFiles();
  
  while(files.hasNext()){
    var file = files.next()
    var fileName = file.getName();
    if (fileName.indexOf('Copy of ') > -1) {
        fileName= fileName.split('Copy of ')[1];
        file.setName(fileName);
    };
  };
}

I reworked this a bit to be fully recursive and to include the parent folder ID.

function fileRename() {
  var parentfolder = DriveApp.getFolderById('XXXXXXXXXXXXXXXXXXXXXXX');
  var recursive = true;

  getFilesFromFolder(parentfolder);

  var folders = parentfolder.getFolders();
  while(folders.hasNext() && recursive){
    var folder = folders.next();
    getFilesFromFolder(folder);
  }
}

function getFilesFromFolder(folder){
  var folderName = folder.getName();
  Logger.log(folderName);
  var files = folder.getFiles();
  while(files.hasNext()){
    var file = files.next()
    var fileName = file.getName();
    if (fileName.indexOf('Copy of ') > -1) {
        Logger.log(fileName);
        fileName= fileName.split('Copy of ')[1];
        file.setName(fileName);
    };
  };
}

Thanks, @edoan! -Saved my day!

I'm using the Chinese version, and my original file is named "a.pdf." After making a copy, the file is named "a.pdf 的副本" (a copy of a.pdf). I can quickly change it back to "a.pdf," but when I download it, the default download filename becomes "a.pdf.pdf 的副本.pdf 的副本" (repeated twice). Does the English version have the same issue? I can't find a way to fix the default download filename.

I'm using the Chinese version, and my original file is named "a.pdf." After making a copy, the file is named "a.pdf 的副本" (a copy of a.pdf). I can quickly change it back to "a.pdf," but when I download it, the default download filename becomes "a.pdf.pdf 的副本.pdf 的副本" (repeated twice). Does the English version have the same issue? I can't find a way to fix the default download filename.

In my comment, the section that rewrites it is this, which should be able to be altered for other languages:

while(files.hasNext()){
    var file = files.next()
    var fileName = file.getName();
    if (fileName.indexOf('Copy of ') > -1) {
        Logger.log(fileName);
        fileName= fileName.split('Copy of ')[1];
        file.setName(fileName);
    };
  };

I can change the name, but when I download it, the default file name is very "ugly". I wonder if I can change the default file name. :(

I asked Google One and they said this problem does not occur in the English version. As for whether it can be solved, I have to report it to google.drive. Thank you all.

That is an excellent script. Below is some updated code you can add to a gsheet script. It adds a menu item to execute the script to the gsheet menu bar and provides a popup box so you can enter the folder name that contains the files with "Copy to " that need to be fixed up.

function onOpen() {
var SS = SpreadsheetApp.getActiveSpreadsheet();
var ui = SpreadsheetApp.getUi();
ui.createMenu('Remove "Copy of" from start of file names in a folder')
.addItem('Start script', 'fileRename')
.addToUi();
};

function fileRename() {
var inputFolder = Browser.inputBox('Enter folder ID', Browser.Buttons.OK_CANCEL);
if (inputFolder === "") {
Browser.msgBox('Remove "Copy of" from the start of file names in this folder:');
return;
}

var folders = DriveApp.getFoldersByName(inputFolder);
var folder = folders.next();
var files = folder.getFiles();
var fileCnt=0;
var renamedCnt = 0;

while(files.hasNext()){
fileCnt++;
var file = files.next()
var fileName = file.getName();
if (fileName.indexOf('Copy of ') > -1) {
fileName= fileName.split('Copy of ')[1];
file.setName(fileName);
renamedCnt++;
};
};
SpreadsheetApp.getUi().alert('Removed "Copy of" from: '+renamedCnt+" Total Files Processed:"+fileCnt);
}

Thank you, it was really useful!