Polymer is modern approach to building web apps. It recently hit the 1.0 milestone and is ready for production. The embedded video is sa great intro to understanding what is polymer and what it can do. Check it out.
On a small note, I tried on polymer about a year ago. I was evaluating it to see if it would fit a proof-of-concept project I had. At that time, it wasn't mature enough (as the devs themselves stated) but I really liked the concept. With the recent "1.0" release, I think it's a good time to start learning it.
Check out polymer: https://www.polymer-project.org