It's no denying that rich Javascript applications (sometimes called single-page applications) are a big thing, but what if you want to leverage Drupal on the backend or have an existing site? Tools like Angular.JS and Backbone are great when you have an API, and with Drupal 8, APIs will be first-class citizens. I'll explore the parts of a single-page application and how to integrate it into either an existing or a new Drupal site, as well as the pitfalls that one must watch out for.