How to insert date into google header using app script? - date

Question

Hello I am trying to set a date into Google Doc's document header. Now, here is the code I got so far but it won't change the current date inside my document's header as I close the document and re-open it any ideas what might be wrong with this code? on the document this is how I have my date: "Daily Report of: 10-19-20"
function onOpen() {
var date = Utilities.formatDate(new Date(), "GMT", "MM-dd-yyyy");
var pattern = "\\d{2}-\\d{2}-\\d{4}";
var header = DocumentApp.getActiveDocument().getHeader();
header.editAsText().replaceText(pattern, date);
}
Also please note that I do have a date in this format inside my header: 15-10-2020. But this should update to give me today's date. However, that's not happening.
Thanks

Answer 1

It is not happening because on your pattern you are looking for a date like 18.10.2020
Instead of using your pattern with . change it to be with -:
var pattern = "\\b\\d{2}\\-\\d{2}\\-\\d{4}\\b";
Also, I would recommend running the script from the Script editor the first time and checking if it works, then doing it by closing and re-opening the document.

Answer 2

I believe your goal as follows.
You want to update the text of 15-10-2020 at the header using var date = Utilities.formatDate(new Date(), "GMT-6", "dd-MM-yyyy") in Google Document using Google Apps Script.
In this case, I would like to propose to modify the value of pattern as follows.
Modified script:
Please modify as follows and test it again.
From:
var pattern = "\\b\\d{2}\\.\\d{2}\\.\\d{4}\\b";
To:
var pattern = "\\d{2}-\\d{2}-\\d{4}";
Added:
From your updated question, it was found that your value on Google Document was Daily Report of: 10-19-20. In this case, how about the following modification?
From:
var pattern = "\\b\\d{2}\\.\\d{2}\\.\\d{4}\\b";
To:
var pattern = "\\d{1,2}-\\d{1,2}-\\d{2,4}";
By this modification, the values of 10-19-20 and 10-19-2020 can be updated.