lucy24 - 12:01 am on Oct 12, 2012 (gmt 0)
mystring = document.getElementById("your-id-here").value
where "value" sounds as if it means "numerical equivalent" but really just means "whatever its content is". If there isn't already code to make sure that your input resolves to an appropriately formatted number, you'll need to do a quick test. After that, you're doing exactly the same thing as
:: insert boilerplate about yawn-provoking coincidence ::
something I posted about less than 24 hours ago.
output = "https://www.example.com/amp;a1=" + mystring
and then plug the "output" variable back into your code using innerHTML or whatever is most appropriate. Can I assume that when you say "amp;" you mean "&"? Or do you really mean "?" (literal question mark)?