Google apps script function work in backend but called by javascript responds undefined

Ok, this is my function.

.gs
function createIfNotExistSheet( name = 'Controller Settings' ) {
  var resp = "";
  try {
    var activeSpreadsheet = SpreadsheetApp.getActiveSpreadsheet();
    var newSheet = activeSpreadsheet.getSheetByName(name);

    if (newSheet == null) {
      newSheet = activeSpreadsheet.insertSheet();
      newSheet.setName(name);
    }
    resp = "Sheet "+ name +" are ready, at id = "+ newSheet.getSheetId();
  }
  catch (e) {
    resp = e;
  }
  finally{
    Logger.log(resp);
    return resp;
  }
}

I call it from js with:

js.
settingsFile = google.script.run.createIfNotExistSheet(cC.settingsFile['name']);

Whether I call it with or without the argument the result does not change, settingsFile returns undefined.