Module example that implemetent a ReactJS form inside a Drupal 8 controller
For detail information about this code read the Blog post http://www.anexusit.com/blog/how-to-load-js-and-css-libraries-a-drupal-8-controller
You could download drupal using composer using the following command.
$ composer create-project drupal-composer/drupal-project:8.x-dev some-dir --stability dev --no-interaction
After that use Drupal Console to install drupal using interactive mode.
$ drupal site:install
Inside your Drupal web directory run the following commands
$ cd /path/to/drupal/web
$ mkdir -p libraries/reactjs/build
$ cd libraries/reactjs/build
$ wget https://unpkg.com/react@15/dist/react.js
$ wget https://unpkg.com/react@15/dist/react.min.js
$ wget https://unpkg.com/react-dom@15/dist/react-dom.js
$ wget https://unpkg.com/react-dom@15/dist/react-dom.min.js
You could change the 15 for the major release of ReactJs that do you need.
Use the following Drupal Console command to install the module
$ drupal module:install mysearch
The module register a new controller in the path /mysearch, use your browser to visit the URL: http://example.com/mysearch.
Enjoy it