Want to create timestamp for time added and create unique incremental user ID. And also include a last changed column

Question

I am using Google Sheets for a (originally planned to be) quick and easy database. Users submit a form, it is then sent to a Sheets for storing.

I have three columns tha

Answer 1

Update from original poster here - I have a solution that isn't the most elegant, but serves my purposes. Criticism & suggestions very much welcome :)

Now on to figuring out the best way to insert dynamic formulas via GAS...

function onChange(e) {

var userId = 1 // column A  
var createdTime = 2 //column B
var lastChangedTime = 24 //column X

var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = e.source.getSheets()[1]; //gets the second sheet

var Avals = ss.getRange("A2:A").getValues(); //gets all the values of column A 
var Alast = Avals.filter(String).length; //puts all values in a string and gets the length

var now = new Date();

if (e.changeType == "INSERT_ROW") {

//set the created time
ss.getActiveSheet().getRange(ss.getActiveRange().getLastRow(), createdTime, 1, 1).setValue(new Date());
//set the userID
ss.getActiveSheet().getRange(ss.getActiveRange().getLastRow(), userId, 1, 1).setValue(Alast+1);

//set lastChangedTime when the row is created 
ss.getActiveSheet().getRange(ss.getActiveRange().getLastRow(), lastChangedTime, 1, 1).setValue(now);
   } 

  if (e.changeType == "EDIT") {

//set date in same row as edit happens, at fixed column  
ss.getActiveSheet().getRange(ss.getActiveRange().getLastRow(), lastChangedTime, 1, 1).setValue(new Date());

   }  
}