Design Principles

Technical architecture and design philosophy of PACE.js.

Philosophy

PACE.js embodies a simple philosophy:

"AI-native storefronts should be as easy to build as static websites, but as powerful as modern web applications."

Core Beliefs

Configuration Over Code - Developers configure, not implement
Convention Over Configuration - Sensible defaults for everything
Progressive Enhancement - Start simple, add complexity as needed
Zero Dependencies - Pure vanilla JavaScript, works everywhere
Framework Agnostic - Integrates with anything
Developer Experience First - 5 minutes to "Hello World"

Design Principles

1. Simplicity First

Problem: Modern frameworks have steep learning curves.

Solution: PACE.js is just JavaScript - if you know HTML/CSS/JS, you know PACE.

javascript

// This is all you need
const pace = new PACE({
  container: '#app',
  products: './products.json'
})

pace.mount()

No build tools. No compilation. No configuration files.

2. Lightweight by Design

Target: < 15KB minified + gzipped

How:

Zero dependencies
Minimal abstractions
Tree-shakeable ES modules
No polyfills (modern browsers only)

Comparison:

React + React DOM: ~42KB
Vue 3: ~34KB
Alpine.js: ~15KB
PACE.js: ~15KB ✅

Why it matters:

Faster page loads
Better mobile performance
Lower bandwidth costs
Improved SEO

3. Pattern-Driven Development

PACE.js encodes the PACE Pattern into reusable code.

The Pattern:

Product       → Discovery & Browse
About         → Context & Trust
Chat          → Guided Assistance
Executive     → Insights & Intelligence

The Framework:

javascript

{
  components: {
    product: ProductCatalog,
    about: AboutPage,
    chat: ChatWidget,
    executiveSummary: ExecutiveSummary
  }
}

Benefit: Developers implement the pattern automatically by using the framework.

4. Configuration Over Code

Traditional approach:

javascript

// 200+ lines of component code
class ProductList extends Component {
  constructor() { ... }
  render() { ... }
  handleClick() { ... }
  // ... more boilerplate
}

PACE approach:

javascript

// 5 lines of configuration
const pace = new PACE({
  container: '#app',
  products: './products.json'
})

95% less code. Same functionality.

5. Progressive Enhancement

Start simple, add features as needed:

Level 1: Minimal

javascript

new PACE({
  container: '#app',
  products: './products.json'
}).mount()

Level 2: Add AI

javascript

new PACE({
  container: '#app',
  products: './products.json',
  aiAdapter: new ClaudeAdapter({ apiKey: '...' })
}).mount()

Level 3: Add Customization

javascript

new PACE({
  container: '#app',
  products: './products.json',
  aiAdapter: new ClaudeAdapter({ apiKey: '...' }),
  theme: { primary: '#3b82f6' },
  greeting: 'Custom greeting',
  plugins: [analyticsPlugin, i18nPlugin]
}).mount()

You never pay for features you don't use.

Architecture

MVC-Inspired Structure

┌─────────────────────────────────────┐
│           PACE Orchestrator         │
│         (Main Controller)           │
└─────────────────────────────────────┘
              ↓
    ┌─────────┼─────────┐
    ↓         ↓         ↓
┌────────┐ ┌──────┐ ┌────────────┐
│ State  │ │Router│ │ Components │
│Manager │ │      │ │            │
└────────┘ └──────┘ └────────────┘
    ↓         ↓         ↓
┌────────────────────────────────┐
│          View Layer            │
│         (HTML/CSS)             │
└────────────────────────────────┘

Separation of concerns:

PACE — Orchestrates everything
State — Manages data
Router — Handles navigation
Components — Render UI

Component Lifecycle

Each component:

Constructs with config
Renders HTML
Attaches event listeners
Responds to user actions
Updates state
Re-renders if needed
Cleans up on destroy

Observer Pattern

State management uses the Observer pattern:

javascript

// State notifies observers when changed
state.set('activeView', 'chat')

// Observers automatically update
state.subscribe('activeView', (newView) => {
  updateUI(newView)
})

Benefits:

Reactive updates
Decoupled components
Easy to reason about
Simple to test

Dependency Injection

Components receive dependencies via constructor:

javascript

class ChatWidget {
  constructor(config, state, aiAdapter) {
    this.config = config      // Configuration
    this.state = state        // Shared state
    this.aiAdapter = aiAdapter // AI provider
  }
}

Benefits:

Testable (inject mocks)
Flexible (swap implementations)
Clear dependencies
No global state

Extensibility

Plugin System

javascript

const analyticsPlugin = {
  name: 'analytics',
  install(pace) {
    pace.on('product:select', ({ product }) => {
      gtag('event', 'product_view', {
        product_id: product.id
      })
    })
  }
}

pace.use(analyticsPlugin)

Plugin capabilities:

Listen to all PACE events
Modify configuration
Add custom components
Extend state
Integrate external services

Adapter Pattern

AI providers are swappable via adapters:

javascript

// Claude
const claude = new ClaudeAdapter({ apiKey: '...' })

// OpenAI
const openai = new OpenAIAdapter({ apiKey: '...' })

// Custom
const custom = new MyCustomAdapter()

// Use any adapter
new PACE({ aiAdapter: claude })

Adapter interface:

typescript

interface AIAdapter {
  sendMessage(message: string, context?: object): Promise<{
    response: string
    metadata?: object
  }>
}

Theme System

Themes use CSS custom properties:

javascript

// JavaScript configuration
new PACE({
  theme: {
    primary: '#3b82f6',
    accent: '#8b5cf6'
  }
})

// Applies CSS variables
:root {
  --pace-primary: #3b82f6;
  --pace-accent: #8b5cf6;
}

Custom themes:

Override CSS variables
Provide custom stylesheets
Extend default styles
Full control over appearance

Integration Patterns

Standalone

html

<div id="app"></div>
<script type="module">
  import { PACE } from 'pace.js'
  new PACE({ container: '#app' }).mount()
</script>

React

tsx

function App() {
  return <PACEWrapper config={{ ... }} />
}

Vue

vue

<template>
  <PACEComponent :config="config" />
</template>

Svelte

svelte

<PACE {config} />

All frameworks supported via wrapper components.

Framework Comparison

vs React

Aspect	React	PACE.js
Size	42KB	15KB
Dependencies	Many	Zero
Learning curve	Steep	Gentle
Build required	Yes	No
Use case	General	Specific (PACE)

When to use:

React — Complex apps, team familiarity
PACE.js — Conversational storefronts

vs Alpine.js

Aspect	Alpine	PACE.js
Size	15KB	15KB
Approach	Reactive attributes	Configuration
Components	None	4 built-in
AI integration	DIY	Built-in
Pattern	None	PACE

When to use:

Alpine — General reactivity
PACE.js — PACE Pattern specifically

Performance

Bundle Size Breakdown

Total: 15KB minified + gzipped

Core:              5KB
State:             2KB
Router:            1KB
Components:        6KB
Utils:             1KB

Benchmarks

Initial load:

Parse time: < 10ms
Time to interactive: < 100ms
First render: < 50ms

Runtime:

State update: < 1ms
Component re-render: < 5ms
Route transition: < 10ms

Tested on M1 MacBook Pro, 4x CPU throttle

Best Practices

1. Keep Components Pure

javascript

// ✅ Good - pure function
render() {
  return `<div>${this.products.map(p => p.name)}</div>`
}

// ❌ Bad - side effects
render() {
  fetch('/api/products') // Side effect!
  return `<div>...</div>`
}

javascript

// ✅ Good
state.set('selectedProduct', product)

// ❌ Bad
window.selectedProduct = product

javascript

// ✅ Good - unsubscribe
const unsub = state.subscribe('view', callback)
return () => unsub()

// ❌ Bad - memory leak
state.subscribe('view', callback)

4. Validate Configuration

javascript

// ✅ Good
if (!config.container) {
  throw new Error('container is required')
}

// ❌ Bad - silent failure
this.container = config.container || '#app'

Security Considerations

XSS Prevention

javascript

// ✅ Good - sanitize user input
const safe = DOMPurify.sanitize(userInput)

// ❌ Bad - raw HTML
innerHTML = userMessage

API Key Protection

javascript

// ✅ Good - environment variables
apiKey: process.env.CLAUDE_API_KEY

// ❌ Bad - hardcoded
apiKey: 'sk-ant-1234567890'

Content Security Policy

html

<meta http-equiv="Content-Security-Policy"
      content="default-src 'self'; script-src 'self' 'unsafe-inline'">

Testing Strategy

Unit Tests

javascript

describe('State', () => {
  it('notifies subscribers', () => {
    const state = new State()
    const spy = jest.fn()

    state.subscribe('key', spy)
    state.set('key', 'value')

    expect(spy).toHaveBeenCalledWith('value', undefined)
  })
})

Integration Tests

javascript

describe('PACE', () => {
  it('renders product catalog', async () => {
    const pace = new PACE({
      container: document.body,
      products: mockProducts
    })

    pace.mount()

    expect(document.querySelector('.pace-product-catalog')).toBeTruthy()
  })
})

Future Enhancements

Planned Features

Server-side rendering — SSR support for Next.js/Nuxt
Streaming responses — Real-time AI responses
Voice interface — Voice input/output
Multi-language — i18n/l10n support
A/B testing — Built-in experimentation
Analytics — First-party analytics

Community Requests

Vue 3 official adapter
Svelte official adapter
WordPress plugin
Shopify integration
Django template tags

Design principles that scale from prototype to production. 🏗️

Design Principles ​

Philosophy ​

Core Beliefs ​

Design Principles ​

1. Simplicity First ​

2. Lightweight by Design ​

3. Pattern-Driven Development ​

4. Configuration Over Code ​

5. Progressive Enhancement ​

Architecture ​

MVC-Inspired Structure ​

Component Lifecycle ​

Observer Pattern ​

Dependency Injection ​

Extensibility ​

Plugin System ​

Adapter Pattern ​

Theme System ​

Integration Patterns ​

Standalone ​

React ​

Vue ​

Svelte ​

Framework Comparison ​

vs React ​

vs Alpine.js ​

Performance ​

Bundle Size Breakdown ​

Benchmarks ​

Best Practices ​

1. Keep Components Pure ​

2. Use State for Sharing ​

3. Subscribe Responsibly ​

4. Validate Configuration ​

Security Considerations ​

XSS Prevention ​

API Key Protection ​

Content Security Policy ​

Testing Strategy ​

Unit Tests ​

Integration Tests ​

Future Enhancements ​

Planned Features ​

Community Requests ​

Design Principles

Philosophy

Core Beliefs

Design Principles

1. Simplicity First

2. Lightweight by Design

3. Pattern-Driven Development

4. Configuration Over Code

5. Progressive Enhancement

Architecture

MVC-Inspired Structure

Component Lifecycle

Observer Pattern

Dependency Injection

Extensibility

Plugin System

Adapter Pattern

Theme System

Integration Patterns

Standalone

React

Vue

Svelte

Framework Comparison

vs React

vs Alpine.js

Performance

Bundle Size Breakdown

Benchmarks

Best Practices

1. Keep Components Pure

2. Use State for Sharing

3. Subscribe Responsibly

4. Validate Configuration

Security Considerations

XSS Prevention

API Key Protection

Content Security Policy

Testing Strategy

Unit Tests

Integration Tests

Future Enhancements

Planned Features

Community Requests