Explore the process of building a reactive multi-user document editor using ScalaJS in this 42-minute conference talk from Scala Days Berlin 2018. Dive into the semantics, challenges, and architecture of creating such an editor, comparing XML and JSON approaches. Learn about data structures, type safety, and the use of tools like Google Web Toolkit and OutWatch. Witness a live demo and gain insights into performance considerations and integration with Eclipse. Discover how to leverage ScalaJS to create responsive, collaborative document editing experiences.