Vue.js

Vue.js (shortened as Vue) is a "progressive, incrementally-adoptable JavaScript framework for building UI on the web."

Why it rocks

 * 1) Very active repository
 * 2) Community support team
 * 3) A programming language very helpful for websites
 * 4) Many companies use this programming language. (such as Apple).
 * 5) It extends HTML to be very useful

Bad Qualities

 * 1) Can be confusing for beginners

Trivia
There is a website that lists some popular websites that use Vue