I'm not sure how the current javascript parser works, but why not embed an
open-source javascript execution engine (mozilla?) in httrack, and when you
parse an "onclick" command in html, call the execution engine with the
required parameters from the html page, then intercept the redirect internally
in javascript and add the redirect to the download queue - instant following
of every javascript link, regardless of how it is written. Apologies if this
is how it is done at the moment.