React is a Javascript framework which lets you write interactive UIs in a declarative way. It lets you design views to represent the state in your application, and it will update and render the right components following changes in the data. The code, however, is much verbose than other frameworks such as Angular. This is based on the asusmption that code is read much more often than writen, therefore, they prefer this approach instead of a more concise one.
Hapi.js and Express solve the same business problem, which is providing an API for HTTP servers in Node.js. Having some conversation with the Javascript gurus at lunch, somebody mentioned Hapi.js. Once I got my eyes on it and its tutorials, it looked pretty similar to Express. Once you start looking at the documentation and examples that both of them provide, and they both have that simple javascript-ish similarity. But the deeper you dive, the more differences you find.
A short introduction to JavaScript promises.
Within this Video Mike speaks about Functional Programming in JavaScript.