onEdit timestamp for specific sheet - google-apps-script

Question

I am looking for help with a script that posts that a specific sheet has been edited rather than when any sheet in the document is modified.
Here is what I currently have:
function onEdit() {
var d = new Date();
var h = d.getHours();
var min = d.getMinutes();
var sec = d.getSeconds();
var h_str = h;
var min_str = min;
var sec_str = sec;
// format time nicely
if (h < 10)
h_str = '0' + h;
if (min < 10)
min_str = '0' + min;
if (sec < 10)
sec_str = '0' + sec;
// create the formatted time string
var time_str = h_str + ':' + min_str + ':' + sec_str;
// create the message
var s = 'Roster last modified on: ' + d.toDateString() + ' # ' + time_str;
// change the range
SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Infernal Dawn').getRange("A1").setValue(s);}
This works perfectly fine to only update the sheet "Infernal Dawn" with the modification date, yet it also updates when ANY sheet is modified.
I found that there were 2 different ways of doing this (one using the gid). The only problem is that my skills in coding are extremely limited and I couldn't figure out how to integrate it into the above code. Any help would be appreciated!

Answer 1

The function onEdit has an optional argument that remembers which cell\range\sheet was edited. The structure of this argument is described here.
function onEdit(e)
{ var d=new Date();
var s=d.toLocaleString();
if(e.source.getActiveSheet().getName()=="TheSheetThatWeWishToTrace")
{ SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Infernal Dawn').getRange("A1").setValue(s);}
}