ProseMirror's document model

 This is a core module of ProseMirror. ProseMirror is a well-behaved rich
 semantic content editor based on contentEditable, with support for
 collaborative editing and custom document schemas.
 .
 This module implements ProseMirror's document model, along with the mechanisms
 needed to support schemas.
 .
 Node.js is an event-based server-side JavaScript engine.