The most important concept to learn about React is the component. React component has internal state, accept props, refs to access the underlying DOM structure, and lifecycle methods.
Don't reinvent the wheel. Ruby Gems I use in almost every project.
Rails 5 required Ruby 2.2 and above. There are ton of new features on Rails 5.
Rails 5.0 released in June 2016 and will only work on Ruby 2.2.1 and above. What's new in Rails 5?