This is a sample script for retrieving the start and end of the month in a year using Google Apps Script and Javascript.
Sample script
function myFunction() {
const year = 2023; // Please set year you expect.
const res = [...Array(12)].map((_, i) =>
[0, 1].map((e) => new Date(year, i + e, 1 - e))
);
console.log(res);
console.log(res.map(([a, b]) => [a.toDateString(), b.toDateString()]));
}
Testing
https://jsfiddle.net/mLrhqwgo/
When this script is run, the following value is obtained with console.log(res.map(([a, b]) => [a.toDateString(), b.toDateString()]))
.
[
["Sun Jan 01 2023", "Tue Jan 31 2023"],
["Wed Feb 01 2023", "Tue Feb 28 2023"],
["Wed Mar 01 2023", "Fri Mar 31 2023"],
["Sat Apr 01 2023", "Sun Apr 30 2023"],
["Mon May 01 2023", "Wed May 31 2023"],
["Thu Jun 01 2023", "Fri Jun 30 2023"],
["Sat Jul 01 2023", "Mon Jul 31 2023"],
["Tue Aug 01 2023", "Thu Aug 31 2023"],
["Fri Sep 01 2023", "Sat Sep 30 2023"],
["Sun Oct 01 2023", "Tue Oct 31 2023"],
["Wed Nov 01 2023", "Thu Nov 30 2023"],
["Fri Dec 01 2023", "Sun Dec 31 2023"]
]