It's a while that I'm trying to learn Rails/Ruby. As I'm a .Net developer by day, I didn't have enough time to learn/master Rails/Ruby. So learning it happened very slowly for me. During this long time I have more time to think about it twice.
For many reasons I'm getting in doubt that if it is better to learn js (or front end development or even Node.js) instead of Rails/Ruby? By now I have a live project mainly developing in js. This project tell me to learn js because it has immediate benefit for it. As a long term ASP.NET developer I've always feeling that I need to know more about front end development. Knowing just server side is not a good idea for today's software development. Single page applications is on trend for some years now. Even mobile software development is easier if knowing js/HTML5. A mainly js application using HTML5 could do many tasks like a native app.
Update: Read article Why The Hell Would I Use Node.js? for getting more information about Node.js.