I got overwhelmed with the number of JS frameworks out there when I started learning recently. At first I was trying to learn EmberJS. Then I thought AngularJS looked cool, so I jumped on that band wagon; React looks interesting too. But I think eventually you just have to choose one and go with it.

Unfortunately I do not know of any that are free. After doing a quick google search for Invision tutorials, I found a series on Digital Tutors, but this is a paid service.

From the development side of things, I really like Invision . It allows the designer to include user interactions to their designs, which makes it that much easier for the developer to implement things. We use this at my company, and it has been extremely helpful and allowed everyone to be on the same page about how a view should look and function; I cannot stress enough how nice it is to be able to show user flows and interaction in the mockups.