google spreadsheets difference

gistfile1

function difference(old_one, new_one){
  var difference = [];
  new_one.forEach(function(new_el){
    var common = false;
    old_one.forEach(function(old_el){
      if(old_el[0] === new_el[0]){
        common = true;
      }
    });
    if(!common){
      difference.push(new_el);
    }
  });
  Logger.log(difference);
  return difference;
}