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:

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);
}