How to create a folder if it doesn't exist?

Question

I'm trying to create a folder if it doesn't exist, but the code creates a new folder every time I run it. I don´t know if my code is right.

Here is my code:

var alumnopath = DocsList.getFolderById ('0Bzgw8SlR34pUbFl5a2tzU2F0SUk');
var alumno2 = alumno.toString();
Logger.log(alumno2);
try {
  var folderalumno =  alumnopath.getFolder(alumno2);
  if (folderalumno == undefined){
    var folderalumno =  alumnopath.createFolder(alumno2);
  }
  else {
    var folderalumno =  alumnopath.getFolder(alumno2);
  }
}
catch(e) {
  var folderalumno =  alumnopath.createFolder(alumno2);
}
folderalumno.createFile(pdf.getAs('application/pdf')).rename(  alumno +  " , " + fechafor);

Thanks for your help!!

Answer 1

As of Google Apps Script code in 2016 Aug

var par_fdr = DriveApp.getFolderById(123456789A); // replace the ID
var fdr_name = "child_fdr";

try {
  var newFdr = par_fdr.getFoldersByName(fdr_name).next();
}
catch(e) {
  var newFdr = par_fdr.createFolder(fdr_name);
}

Answer 2

You actually don't need the if condition when you use a try/catch structure. The try/catch structure handles the case where the folder doesn't exist by itself.

Try it like this:

var alumnopath = DocsList.getFolderById ('0Bzgw8SlR34pUbFl5a2tzU2F0SUk');
var alumno2 = alumno.toString();
Logger.log(alumno2);
try{
  var folderalumno =  alumnopath.getFolder(alumno2);
}
catch(e) {
  var folderalumno =  alumnopath.createFolder(alumno2);
}
folderalumno.createFile(pdf.getAs('application/pdf')).rename(  alumno +  " , " + fechafor);

Answer 3

In case anyone else runs in to this issue, you can use the ternary operator like this (replacing the "Name_of_Folder" string as needed):

var alumnopath = DriveApp.getFoldersByName("Name_of_Folder");
var folderalumno = alumnopath.hasNext() ? 
    alumnopath.next() : DriveApp.createFolder("Name_of_Folder");