Find & replace in files within a folder using Google Apps Script http://stackoverflow.com/questions/20510314/find-replace-in-files-within-a-folder-using-google-apps-script

Find & replace in files within a folder using Google Apps Script.js

//  Iterate through the file iterator for a particular folder

function iterateFolderById() {
  var files = DriveApp.getFolderById("0B5eEwPQVn6GOaUt6Vm1GVjZmSTQ").getFiles();
  while (files.hasNext()) {
    var file = files.next();
    Logger.log(file.getName());
    var doc = DocumentApp.openById(file.getId());
   doc.replaceText("My search string or regex", "My replacement string");
 }
 Logger.log("Done")
}

// Find folder by its name

function processFoldersByName() {
  var folders = DriveApp.getFoldersByName("myfoldername");
  var myFolder = null;
  if (folders.hasNext())
    myFolder = folders.next();
  if (myFolder !== null) {
    // do stuff
  } else {
    // exit gracefully
  }
}

//  if you have multiple folders with the same name, you would have to iterate through them in a while loop
// (similar to the file iterator in the code you linked) and find a marker that proves this is the folder 
// you are looking for (i.e. you could have an empty file with a particular name in there)

// By patt0, http://stackoverflow.com/questions/20510314/find-replace-in-files-within-a-folder-using-google-apps-script