App Script to send the response from Google Form to Firebase

Form.gs

function onFormSubmit(e) {
  var form = FormApp.openById('1Z65umQSZ2drz3MvTWCWlwP4-ySeoB5D7RvX1LtusnEU');
  var formResponses = form.getResponses();
  var latestResponse = formResponses.length - 1;
  var formResponse = formResponses[latestResponse];
  
  var email = formResponse.getRespondentEmail();
  
  var items = formResponse.getItemResponses();
  
  
  var name = getMethod(items[3]);
  var phone = getMethod(items[4]);
  var flat = getMethod(items[5]);
  var area = getMethod(items[6]);
  var item = getMethod(items[0]).toString();
  var quantity = getMethod(items[1]);
  var suggestion = getMethod(items[7]);
  
  var dataToExport = {};
  
  dataToExport = 
    {  
      "name": name,
      "email":email,
      "phone":phone,
      "address":
      { 
        "flat":flat,
        "area":area
      },
      "item": item,
      "quantity": quantity,
      "suggestion": suggestion
    };

  Logger.log(getMethod(items[0]));
  
  var dateStr = getMethod(items[2]);
  var date = Utilities.formatDate(new Date(dateStr), "GMT+1", "yyyyMMdd");
                                  
  var base = FirebaseApp.getDatabaseByUrl('https://sendingresponse-64495.firebaseio.com/');
  base.setData("orders/"+date+"/"+phone, dataToExport);
}

function getMethod(item) {
  var value = item || "_unknown_"; // if null then "_unknown_" is assigned
  
  function check(x) {
    if(x == "")
      return "_unknown_";
    else 
      return x;
  }
  
  if(value != "_unknown_") {
    return check(value.getResponse());
  } else {
    return value;
  }
}