Depends on the industry/area. In SFBay a talented javascripter can command as much as a talented Rubyist if you are willing to work at a startup. Bonus points if you also have a graphic design or UX chops.
The move from AS to JS is also not going to be as big a jump. Further, if you are taking a pay cut to shift stacks then I would suggest that you are getting in on new stacks too late.
The thing you have to remember is supply and demand. Companies will pay you when supply is low, since they are in need of good talent. If you're a good negotiator - like myself, you can write your own ticket.