As many of you know, part of the REST api was added to WordPress core in version 4.4. The endpoints are not there yet, but you can install the plugin https://wordpress.org/plugins/json-rest-api/ which works seemlessly with core and steps out of the way as new core features are introduced.
For those of us who were already running a REST api from our sites using the plugin, this core change does not mean a whole lot. However, what it does do is begin the process of adding REST api support to everyone else’s sites. With WordPress usage growing exponentially through the web is now very common to find WordPress being used for most sites we visit. Once the api is completely integrated within core, we will be able to pull data from any of these site using the same structure on each site. This means building an api parser once and simply changing the domain to reuse. There will always be custom implementations of data throughout sites but the main data will be the same.
Another framework that is gaining popularity is React JS. Being backed by Facebook is certainly helping this framework to catch notice. What I find most inspiring about this framework is it is JSON data driven. You are able to render you site/apps components using JSON data from an api endpoint. The WordPress api serves JSON data so it feels like they were designed to work together.
The value of React JS has grown greatly because of the WordPress api integration. We can now build universal interfaces and apps with React JS that will work with any WordPress site. Well, not quite yet but very soon. WordPress.com is already running their dashboard on React JS and the WordPress api.
If you are new to React JS, there are a ton of tutorials on the web but I found personally the easiest guides to follow were the ones on the official React JS website https://facebook.github.io/react/docs/getting-started.html. I also personally prefer to run it within a Grunt watch task and use Babel to compile the JSX.
Welcome to the future!