What does the javascript tab character do?

I found an old discussion that you might find interesting for understanding the possible historical reasons behind this choice.

That's a 19-year-old bug in Mozilla. The problem was that one website was not working as expected, because Mozilla didn't strip tab characters inside the URL in a link. The page worked as expected in Internet Explorer, which apparently ignored the javascript tab character. Tabs are often used for indentation in HTML files, so sometimes you can expect a few tabs after a new line. Somebody cited a IETF standard suggesting that "whitespace should be ignored when extracting the URI". However, others were not fully convinced that removing all whitespace characters would be a good idea, because sometimes you might run across URIs with unencoded spaces (for example: https://www.example.com/path with spaces/), even though that would be wrong, at least according to current standards. Therefore they decided to just add tabs to the list of removed characters (carriage-return and line-feed characters were already being removed). Note though that spaces are allowed, and ignored, when they are at the beginning or at the end of the URI (example: ).

So I suppose the historical reason for this choice is that they wanted to make sure the following code would work:

However they did not check exactly where the spaces or tabs were in the URL, they just decided to keep the spaces and remove the tabs. As a result, the first example doesn't work if you use spaces for indentation, and tab characters can be included anywhere in the URL without affecting anything (so even javascript will be ok).