Cleint Side Programing AS3 or JS ?

I am not a programing guru but I know a ting or two about web programing and I am at a point where I have to ask myself one question. I already know ActionScript 3 a bit, I learn it in Flex 2.0 and now I can pull out a nice interface and cool dynamic elements with it. Now when I started to learn PHP and XHTML, CSS, I found myself learning JavaScript also. Is it really necessary, in your opinion, to learn JavaScript if I already know ActionScript?

I knw javascript and there is on compusalry tht u need to knw actionscript 3 tht come sin flash side.. nt sure on tht ...though.

According to me action script is for the flash and java script is for client side html pages. So both are different things. For website javascript is necessary I think