Recently came across this article and the point to note is that everyone here speaks about side projects. So how important are they? If you have an idea, working on it helps validate it. You can try new technologies and learn a lot building it. Side projects are important because you know what you are building and it is a lot easier to explain it to someone about it. Also you would be building something because you are passionate about it. A project at work may not be that interesting, so to keep your passion alive, a side project may do the trick.
Programming is something that you cannot learn once and use it over and over again. There are ocean full of opportunities and possibilities. And learning in this profession is a never ending deal. Also reading a book or watching a screencast will not help in long run, if you have not actually sit down and written a piece of code. So it boils down to creating of Side projects.
These days it is angular js that is very popular in the front end dev community. Tomorrow there may be some other technology. However the bottom line is that one has to know how things work and should have a good logical, analytical skill set to grasp new topics very quickly.
I had also come across one article, forgot to bookmark that link, it was on hacker news. The article put across very interesting concept that we should document everything that we do. In blog post, over github or anything you feel comfortable. The moment you realise that you are asking a question to google, make it a point to note it down and write an answer to it that worked for you. Doing this will not only leave a digital print but also will help you remember in future and you will always have reference to the solution if in case you encounter the same problem in future. I really like this idea and I feel that such activities are very important.