Ask HN: How to Transition from Back End to Front End?

I've been doing web development for about 2-3 years now and have been looking to expand my skills. I've mostly worked on the back-end side of things (java, scala, etc..), but have also done quite a bit of front end work. I know quite a bit of JavaScript (although still learning) and have been getting alot of experience with Node.js too.

The problem is that in all my jobs, the teams have basically worked with Jquery (was sort of hacked together spaghetti). I've recently been working a bit with React and Backbone, but feel like I'm just piecing together random tutorials on the internet. I think it's time to take the dive and try to learn how to be a Front End developer on a truly professional level. At this point I feel like just flipping a coin to choose between the crazy amount of frameworks and digging deep into it.

Does anyone have any recommended learning path to transition from the back end to the front end?

Particularly someone who's moderately comfortable with JavaScript, HTML/CSS, etc.. (ie. not completely new, but wants to level up to the professional level)