Trying to generate a unique code for every form reply

Question

I am having some trouble getting a script that can generate a unique code for every form reply entry to work. Now, when I first tried writing it, I used the function name onFormReply(e) since I had read it somewhere, but turn out it didn't really work, so I'm trying to use onEdit(e), but it marks most values of the variables I wrote as undefined, even the argument (e) of the function itself (which is theoretically suposed to be custom and made to resemble the cell/s where the edit took place). Here is the code:

    function onEdit(e) {
  const ss = SpreadsheetApp.getActiveSheet();
  const row = e.getRow();
  


  var date = ss.getRange(row,1).getValue();


  var department = ss.getRange(row,6).getValue();
  department = department[0] + department[1]


  var uniqueNumber = ss.getLastRow()


  var finalCode = department + finalDate + uniqueNumber


  ss.getRange(row,15).setValue(finalCode)
}

Answer 1

If you are dealing with Google Form responses, you can use the timestamp in column A as a unique ID. These timestamps are accurate down to the millisecond and will for all practical purposes always be unique.

The great benefit of this is that you do not need a script to get those unique IDs. Instead, use this array formula in row 1 of a free column in the right in the form responses sheet:

=arrayformula( 
  { 
    "Unique ID"; 
    iferror( text( 1 / A2:A ^ -1, "yyyy-MM-dd_HH-mm-ss-000") ) 
  } 
)

The formula will fill the whole column automatically and will continue giving more results as new form responses are submitted.