Frankly speaking, this might be a wrong forum if you want to turn into Web Designers. Most of the people here are programmers (web developers like you). AFAIK, knowledge of JS will give you an edge as a web designer, but does not make you one. Ofcourse, you need to have design knowledge. And remember, like engineering, design is a science.
You also need to ask yourself, what is it which motivates you to become a designer? Do you think you are one of those, who are born with a taste (I wish I was one :()
Anyway, off topic but this one has a nice comparision between a developer and a designer.
http://sixrevisions.com/infographs/web-designers-vs-web-developers/[
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