Auto-updating timestamp [duplicate]

Question

In a particular cell of a column, I would like to have a timestamp of the last date any cell of that column was modified. Specifically: G31 would show a date of last modification on any cell of the G column.

My question is quite similar to this one, but I can't seem to apply it to my situation :
Auto-updating column in Google Spreadsheet showing last modify date

I have tried this :

function onEdit() 
{ var DEVIS_COMPLET_2018 = "MySheet"; 
var s = SpreadsheetApp.getActiveSheet(); 
if (s.getName() !== DEVIS_COMPLET_2018) return; 
var r = s.getActiveCell(); 
if( r.getColumn() != G ) { //checks the column 
var row = r.getRow(); 
var time = new Date(); 
time = Utilities.formatDate(time, "GMT-08:00", "MM/DD/yy");
SpreadsheetApp.getActiveSheet().getRange('G31').setValue(time); }; }; 

I don't get any error message but nothing happens.

I have tried enclosing G, still no luck :

function onEdit() {
var DEVIS_COMPLET_2018 = "MySheet";
var s = SpreadsheetApp.getActiveSheet();
if (s.getName() !== DEVIS_COMPLET_2018) return;
var r = s.getActiveCell();
if( r.getColumn() != "G" ) { //checks the column
var row = r.getRow();
var time = new Date();
time = Utilities.formatDate(time, "GMT-08:00", "MM/DD/YY");
SpreadsheetApp.getActiveSheet().getRange("G31").setValue(time); }; };

Answer 1

Try

function onEdit(e) {
var sh = e.range.getSheet(); //sheet    
if (sh.getName() !="DEVIS_COMPLET_2018" || e.range.columnStart != 7 ) { return; }
sh.getRange("G31").setValue(new Date());
}

Answer 2

The script apparently does nothing because the condition (r.getColumn() != G)

• getColumn() returns an integer
• G, as it's not quote enclosed it's considered a variable name. As it's not declared previously it returns undefined.

Another possible problem is on time = Utilities.formatDate(time, "GMT-08:00", "MM/DD/yy"); The problem is that DD will return the day on the year instead the day on the month.

Answer 3

function onEdit() {
  var sheetName = "Sheet1";
  var s = SpreadsheetApp.getActiveSheet();
  if (s.getName() !== sheetName) return;
  var r = s.getActiveCell();
  if( r.getColumn() != 7 ) { //checks the column
    var row = r.getRow();
    var time = new Date();
    time = Utilities.formatDate(time, "GMT-08:00", "MM/dd/yy");
    SpreadsheetApp.getActiveSheet().getRange('G31').setValue(time);
  };
 };