Originally built in Handlebars with Backbone, in 2016 the dispersed development team behind Plex (including remote freelancers like me) began to introduce React into the mix.
This began with simple but subtle UI enhancements: introducing nice pieces of animation and features such as zoom for media grids. By the end of the following year the platform had undergone a comprehensive and completed reworking, discarding Handlebars altogether and introducing some of the meatier pieces of work we undertook, including an all-new media player handling both audio and video from a single component.