Collaborative Whiteboard

A real-time collaborative whiteboard application built with Node.js, Express, and Socket.IO with modular architecture.

Features

• Real-Time Drawing: Click and drag to draw lines on a shared canvas
• Color Selection: 10-color palette with visual selection feedback
• Brush Size Control: Adjustable brush size from 1-20px
• Clear Canvas: Reset the canvas for all connected users
• Real-Time Synchronization: All drawing actions are instantly visible to all connected clients
• Multi-User Support: Multiple users can draw simultaneously without conflicts
• Connection Status: Clear visual indicator with red/green status dot
• User Management: User count display and individual socket IDs
• Undo Functionality: Local undo for user's own drawings
• Responsive Design: Works on desktop, tablet, and mobile screens
• Modular Architecture: Clean separation of concerns with dedicated managers
• Test-Driven Development: Comprehensive test suite with 67 passing tests

Development Status ✅ COMPLETED

✅ Phase 1: Foundation & Connection

• Express server serving static files
• Socket.IO connection established
• Basic client-server communication

✅ Phase 2: Core Drawing & Real-Time Synchronization

• Mouse event handling for canvas drawing
• Drawing data structure and protocol
• Real-time broadcast of drawing events
• Multi-client drawing synchronization

✅ Phase 3: Enhanced Features

• Color picker with 10 color options
• Brush size slider (1-20px range)
• Clear canvas button with synchronization across all users
• Professional UI with animations and visual feedback
• Connection status indicators with proper coloring
• User count display and user IDs
• Undo functionality (local)

✅ Phase 4: Polish & Optimization

• Modular Architecture: StateManager, CanvasManager, SocketManager, UIManager
• Performance Optimization: Efficient event handling and rendering
• Enhanced Error Handling: Graceful disconnection/reconnection
• Code Documentation: Comprehensive comments and structure
• Testing: 67 tests全部通过 across 11 test suites
• Production Readiness: Clean codebase with proper .gitignore

Technology Stack

• Backend: Node.js, Express, Socket.IO
• Frontend: HTML5 Canvas, Vanilla JavaScript (ES6+), CSS3
• Architecture: Modular design with separation of concerns
• Testing: Jest for comprehensive test coverage
• Development: nodemon for auto-restart during development
• Styling: Font Awesome icons, custom CSS with animations and transitions

Modular Architecture

Core Modules:

1. StateManager.js - Centralized application state management

   • Manages drawing history, user state, application properties
   • Provides consistent state access and updates

2. CanvasManager.js - Drawing operations and canvas handling

   • Mouse/touch event handling
   • Drawing rendering and canvas manipulation
   • Coordinate calculations and drawing logic

3. SocketManager.js - Real-time network communication

   • Socket.IO connection management
   • Event emission and listening
   • Network error handling and reconnection

4. UIManager.js - User interface and controls

   • DOM element caching and updates
   • Control event handling (colors, brush size, clear, undo)
   • Connection status display and user feedback

Application Orchestrator:

• app.js - Main application file that initializes and connects all modules
• Follows the mediator pattern for clean module communication