Project 08: Collaborative Document Editor

Collaborative editing is one of the hardest problems in web development. Think about Google Docs - multiple people typing at the same time, and everyone sees changes instantly. This is advanced but valuable knowledge.

You'll learn operational transformation or CRDTs, which are algorithms that handle conflicts when two people edit the same text at the same time. These concepts are used in many collaboration tools.

This project teaches you how to handle complex state synchronization. Version history, conflict resolution, and autosave are all challenging features that will push your skills to the next level.

Collaborative editing is complex but powerful. Think Google Docs, Notion, or Figma - multiple people editing the same thing at the same time. This is advanced but impressive when you can build it.

This project teaches conflict resolution. When two people type at the same time, the system needs to merge their changes without losing data. This is called operational transformation or CRDTs.

You'll learn about version history, which lets users undo changes or see what changed over time. These skills apply to any collaborative software, not just document editors.

Create a collaborative document editor similar to Google Docs where multiple users can edit the same document simultaneously. This project introduces operational transformation, conflict resolution, version history, and complex state synchronization across multiple clients.

Implement real-time collaborative editing

Handle conflict resolution when multiple users edit simultaneously

Build version history and revision tracking

Create autosave functionality

Manage cursor positions across clients

Implement operational transformation or CRDTs

Document: id, title, content (JSON or plain text), ownerId, createdAt, updatedAt

Version: id, documentId, content, author, timestamp, changeDescription

Permission: documentId, userId, role (owner/editor/viewer)

ActiveUser: documentId, userId, cursorPosition, lastSeen

join_document - User opens document for editing

leave_document - User closes document

text_change - User makes an edit (send operation)

cursor_move - User moves cursor

save_document - Manual save triggered

user_joined - Notify others when new user joins

user_left - Notify others when user leaves

POST /api/documents - Create new document

GET /api/documents - Get user's documents

GET /api/documents/:id - Get document content

PUT /api/documents/:id - Update document (autosave)

DELETE /api/documents/:id - Delete document

GET /api/documents/:id/versions - Get version history

POST /api/documents/:id/restore - Restore specific version

POST /api/documents/:id/share - Share with user

GET /api/documents/:id/collaborators - Get all collaborators

Document list page showing all accessible documents

Rich text editor using Draft.js, Slate, or Quill

Formatting toolbar (bold, italic, headings, lists)

Active users indicator with avatars

Colored cursors showing where others are typing

Save status indicator (saved, saving, unsaved changes)

Version history sidebar with timestamps and authors

Share modal with email input and permission selector

Conflict notification when simultaneous edits occur

Implement operational transformation to handle concurrent edits

Broadcast changes to all connected clients efficiently

Track cursor positions and transform them with content changes

Implement debounced autosave to reduce database writes

Store document state in memory for active editing sessions

Handle network disconnections gracefully

Queue operations while offline and replay on reconnect

Create snapshots periodically to prevent long replay chains

Each edit operation includes position and content

Transform incoming operations based on pending operations

Use vector clocks or timestamps to order operations

Last write wins for same position (with user notification)

Maintain operation history for debugging conflicts

Add comments and suggestions mode

Implement text highlighting and annotations

Add document templates

Create presentation mode for documents

Implement document export to PDF or Markdown

Add table support in editor

Implement image insertion and management

Add change tracking with accept/reject workflow

Multiple users can edit simultaneously without data loss

Changes appear in real-time for all users

Cursor positions update correctly

Autosave works reliably every 30 seconds

Version history accurately tracks all changes

Restoring previous versions works correctly

Offline mode queues changes and syncs on reconnect

No conflicts result in lost edits

Study operational transformation algorithms

Research CRDT (Conflict-free Replicated Data Types)

Explore Yjs or Automerge libraries

Learn about rich text editor libraries (Slate, Draft.js, Quill)

Look into ShareDB for real-time collaboration