---
name: zero-build-frontend
description: Zero-build frontend development with CDN-loaded React, Tailwind CSS, and vanilla JavaScript. Use when building static web apps without bundlers, creating Leaflet maps, integrating Google Sheets as database, or developing browser extensions. Covers patterns from rosen-frontend, NJCIC map, and PocketLink projects.
---

# Zero-build frontend development

Patterns for building production-quality web applications without build tools, bundlers, or complex toolchains.

## Picking a stack

Three current zero-build approaches, each with different trade-offs:

| Stack | When | Bundle size impact |
|---|---|---|
| **React via esm.sh + htm** | Component-heavy SPAs, existing React mental model, Tailwind styling | ~50 KB gzipped (React + ReactDOM + htm) |
| **htmx 2.x + server-rendered HTML** | CRUD apps, traditional MPA flow, want server-side state of truth | ~14 KB gzipped (htmx alone) |
| **Alpine.js 3.x + plain HTML** | Light interactivity sprinkled into mostly-static pages, no full SPA | ~15 KB gzipped (Alpine alone) |

You can mix htmx and Alpine.js in the same page — htmx handles server interactions, Alpine handles client-side UI state. Many production sites converge on this combo.

## ESM import maps

Import maps let you write `import x from 'react'` in a `<script type="module">` without a bundler — the browser resolves the bare specifier against the map. Stable in all major browsers since 2023.

```html
<script type="importmap">
{
  "imports": {
    "react": "https://esm.sh/react@19.0.0",
    "react-dom/client": "https://esm.sh/react-dom@19.0.0/client",
    "lodash-es": "https://esm.sh/lodash-es@4.17.21",
    "@my-app/": "/src/"
  },
  "scopes": {
    "https://esm.sh/": {
      "scheduler": "https://esm.sh/scheduler@0.23.0"
    }
  }
}
</script>
```

The `scopes` block lets a sub-tree of imports resolve differently. Useful when one CDN package needs a specific transitive dependency. The trailing `/` form (`"@my-app/": "/src/"`) lets you import any file under that prefix.

**Pin versions in production.** `esm.sh/react` (without a version) and `esm.sh/react@latest` resolve at request time and can shift under you. Use exact pinned versions or SHA-locked URLs.

## htmx 2.x — server-rendered interactivity

htmx 2.0 (released June 2024) lets you add AJAX, WebSockets, and SSE to plain HTML through `hx-*` attributes. The server sends HTML fragments; the client swaps them in. No JS framework required.

```html
<script src="https://unpkg.com/htmx.org@2.0.4"></script>

<!-- Click button → POST to server → swap response into #result -->
<button hx-post="/api/clicked" hx-target="#result" hx-swap="innerHTML">
  Click me
</button>
<div id="result"></div>

<!-- Search-as-you-type with debounce -->
<input
  type="search"
  name="q"
  hx-get="/api/search"
  hx-trigger="input changed delay:300ms"
  hx-target="#results"
/>
<div id="results"></div>

<!-- Infinite scroll -->
<div hx-get="/api/items?page=2"
     hx-trigger="revealed"
     hx-swap="afterend">
  ...
</div>
```

htmx 2.x dropped IE support and tightened the API; if you're on htmx 1.x and don't need to migrate, 1.x still receives security patches. New code should target 2.x.

## Alpine.js 3.x — client-side reactivity in HTML

Alpine.js (current 3.14+) is a minimal alternative to Vue/React for sprinkles of interactivity. State and behavior live as `x-*` attributes in the markup.

```html
<script defer src="https://unpkg.com/alpinejs@3.14.1/dist/cdn.min.js"></script>

<!-- Toggle visibility -->
<div x-data="{ open: false }">
  <button @click="open = !open">Toggle</button>
  <div x-show="open" x-transition>Content here</div>
</div>

<!-- Two-way binding + computed -->
<div x-data="{ first: '', last: '' }">
  <input x-model="first" placeholder="First">
  <input x-model="last" placeholder="Last">
  <p x-text="`Hello, ${first} ${last}`"></p>
</div>

<!-- Fetch on mount -->
<div x-data="{ items: [] }"
     x-init="items = await (await fetch('/api/items')).json()">
  <template x-for="item in items" :key="item.id">
    <li x-text="item.title"></li>
  </template>
</div>
```

Alpine pairs naturally with htmx: htmx swaps a server-rendered fragment in, Alpine handles whatever client-side state that fragment needs (open/close, optimistic toggles, form validation).

## React via CDN (esm.sh)

### Basic setup

```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Zero-Build React App</title>

  <!-- Tailwind CSS via CDN.
       cdn.tailwindcss.com is the Play CDN; Tailwind explicitly recommends
       it for prototyping only — it ships an in-browser JIT compiler that
       runs at every page load. For production, use the standalone CLI
       binary or the Vite/PostCSS plugin. Tailwind 4 (released Jan 2025)
       is the current major; the Play CDN serves v3 by default. -->
  <script src="https://cdn.tailwindcss.com"></script>
  <script>
    tailwind.config = {
      theme: {
        extend: {
          fontFamily: {
            display: ['Special Elite', 'monospace'],
            body: ['Roboto Mono', 'monospace'],
          },
          colors: {
            brand: {
              primary: '#2dc8d2',
              secondary: '#f34213',
              dark: '#183642',
            }
          }
        }
      }
    }
  </script>

  <!-- Google Fonts -->
  <link href="https://fonts.googleapis.com/css2?family=Special+Elite&family=Roboto+Mono:wght@400;500;700&display=swap" rel="stylesheet">

  <!-- Custom styles -->
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <div id="root"></div>

  <!-- ES Module imports.
       React 19 (Dec 2024) is the current major; 18.x still works fine
       for sites that pin to it. Pin a specific version in production —
       don't ship `react@latest`, since esm.sh resolves at request time. -->
  <script type="importmap">
  {
    "imports": {
      "react": "https://esm.sh/react@19.0.0",
      "react-dom/client": "https://esm.sh/react-dom@19.0.0/client",
      "htm": "https://esm.sh/htm@3.1.1"
    }
  }
  </script>

  <script type="module" src="index.js"></script>
</body>
</html>
```

### React with htm (no JSX, no build)

```javascript
// index.js
import React, { useState, useEffect, useRef } from 'react';
import { createRoot } from 'react-dom/client';
import htm from 'htm';

// Bind htm to React.createElement
const html = htm.bind(React.createElement);

// Components use html`` instead of JSX
function App() {
  const [records, setRecords] = useState([]);
  const [loading, setLoading] = useState(true);
  const [search, setSearch] = useState('');

  useEffect(() => {
    loadData();
  }, []);

  async function loadData() {
    try {
      const response = await fetch('data/archive-data.json');
      const data = await response.json();
      setRecords(data.records);
    } catch (error) {
      console.error('Failed to load data:', error);
    } finally {
      setLoading(false);
    }
  }

  const filtered = records.filter(r =>
    r.title.toLowerCase().includes(search.toLowerCase())
  );

  if (loading) {
    return html`<div class="flex items-center justify-center h-screen">
      <div class="animate-spin w-8 h-8 border-4 border-brand-primary border-t-transparent rounded-full"></div>
    </div>`;
  }

  return html`
    <div class="min-h-screen bg-gray-900 text-white">
      <header class="p-4 border-b border-gray-700">
        <h1 class="font-display text-2xl">Archive Explorer</h1>
        <input
          type="text"
          placeholder="Search records..."
          value=${search}
          onInput=${(e) => setSearch(e.target.value)}
          class="mt-2 w-full p-2 bg-gray-800 rounded border border-gray-600 focus:border-brand-primary outline-none"
        />
      </header>

      <main class="p-4">
        <${RecordList} records=${filtered} />
      </main>
    </div>
  `;
}

function RecordList({ records }) {
  return html`
    <div class="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
      ${records.map(record => html`
        <${RecordCard} key=${record.id} record=${record} />
      `)}
    </div>
  `;
}

function RecordCard({ record }) {
  return html`
    <article class="p-4 bg-gray-800 rounded-lg border border-gray-700 hover:border-brand-primary transition-colors">
      <h2 class="font-display text-lg mb-2">${record.title}</h2>
      <p class="text-sm text-gray-400 mb-2">${record.publication_date}</p>
      <p class="text-sm line-clamp-3">${record.summary}</p>
      <div class="mt-2 flex flex-wrap gap-1">
        ${record.tags?.map(tag => html`
          <span key=${tag} class="px-2 py-1 text-xs bg-gray-700 rounded">${tag}</span>
        `)}
      </div>
    </article>
  `;
}

// Mount app
const root = createRoot(document.getElementById('root'));
root.render(html`<${App} />`);
```

## Data caching with localStorage

```javascript
// services/cacheService.js

const CACHE_TTL = 60 * 60 * 1000; // 1 hour

export function getCached(key) {
  const cached = localStorage.getItem(key);
  if (!cached) return null;

  try {
    const { data, timestamp } = JSON.parse(cached);
    if (Date.now() - timestamp > CACHE_TTL) {
      localStorage.removeItem(key);
      return null;
    }
    return data;
  } catch {
    localStorage.removeItem(key);
    return null;
  }
}

export function setCache(key, data) {
  localStorage.setItem(key, JSON.stringify({
    data,
    timestamp: Date.now()
  }));
}

export async function fetchWithCache(url, cacheKey) {
  // Check cache first
  const cached = getCached(cacheKey);
  if (cached) return cached;

  // Fetch fresh data
  const response = await fetch(url);
  const data = await response.json();

  // Cache for next time
  setCache(cacheKey, data);

  return data;
}

// Usage
const records = await fetchWithCache('data/archive-data.json', 'archive-records');
```

## Leaflet.js maps

### Basic map setup

```html
<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.4/dist/leaflet.css" />
  <link rel="stylesheet" href="https://unpkg.com/leaflet.markercluster@1.4.1/dist/MarkerCluster.css" />
  <link rel="stylesheet" href="https://unpkg.com/leaflet.markercluster@1.4.1/dist/MarkerCluster.Default.css" />
  <style>
    #map { height: 85vh; width: 100%; }
  </style>
</head>
<body>
  <div id="map"></div>

  <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"></script>
  <script src="https://unpkg.com/leaflet.markercluster@1.4.1/dist/leaflet.markercluster.js"></script>
  <script src="js/app.js"></script>
</body>
</html>
```

### Map application with clustering

```javascript
// js/app.js

class MapApp {
  constructor() {
    this.map = null;
    this.markers = null;
    this.data = [];
    this.filters = {
      year: null,
      county: null,
      status: null
    };
  }

  async init() {
    this.setupMap();
    await this.loadData();
    this.renderMarkers();
    this.setupFilters();
  }

  setupMap() {
    // Initialize map centered on NJ
    this.map = L.map('map', {
      center: [40.0583, -74.4057],
      zoom: 8,
      scrollWheelZoom: false,  // Disable mouse wheel zoom
      zoomControl: false       // We'll add custom controls
    });

    // Add tile layer (CARTO Voyager)
    L.tileLayer('https://{s}.basemaps.cartocdn.com/rastertiles/voyager/{z}/{x}/{y}{r}.png', {
      attribution: '&copy; OpenStreetMap, &copy; CARTO',
      maxZoom: 19
    }).addTo(this.map);

    // Add custom zoom control (top-right)
    L.control.zoom({ position: 'topright' }).addTo(this.map);

    // Initialize marker cluster group
    this.markers = L.markerClusterGroup({
      spiderfyOnMaxZoom: true,
      showCoverageOnHover: false,
      maxClusterRadius: 50,
      spiderLegPolylineOptions: { weight: 1.5, color: '#2dc8d2' }
    });

    this.map.addLayer(this.markers);
  }

  async loadData() {
    const response = await fetch('data/grantees.json');
    this.data = await response.json();
  }

  renderMarkers() {
    this.markers.clearLayers();

    const filtered = this.data.filter(item => {
      if (this.filters.year && item.year !== this.filters.year) return false;
      if (this.filters.county && item.county !== this.filters.county) return false;
      if (this.filters.status && item.status !== this.filters.status) return false;
      return true;
    });

    filtered.forEach(item => {
      if (!item.lat || !item.lng) return;

      const marker = L.marker([item.lat, item.lng], {
        icon: this.createIcon(item.status)
      });

      marker.bindPopup(this.createPopup(item));
      this.markers.addLayer(marker);
    });

    // Update count display
    document.getElementById('count').textContent = filtered.length;
  }

  createIcon(status) {
    const colors = {
      'Active': '#2dc8d2',
      'Completed': '#666666',
      'Pending': '#f34213'
    };

    return L.divIcon({
      html: `<div style="background: ${colors[status] || '#2dc8d2'}; width: 12px; height: 12px; border-radius: 50%; border: 2px solid white;"></div>`,
      className: 'custom-marker',
      iconSize: [16, 16],
      iconAnchor: [8, 8]
    });
  }

  createPopup(item) {
    return `
      <div class="popup-content">
        <h3 class="font-bold text-lg">${item.name}</h3>
        <p class="text-sm text-gray-600">${item.county} County</p>
        <p class="text-sm mt-2">${item.description || ''}</p>
        <div class="mt-2">
          <span class="px-2 py-1 text-xs rounded bg-gray-200">${item.status}</span>
          <span class="px-2 py-1 text-xs rounded bg-gray-200">${item.year}</span>
        </div>
        ${item.website ? `<a href="${item.website}" target="_blank" class="block mt-2 text-brand-primary">Visit Website →</a>` : ''}
      </div>
    `;
  }

  setupFilters() {
    // Year filter
    const years = [...new Set(this.data.map(d => d.year))].sort();
    const yearSelect = document.getElementById('year-filter');
    years.forEach(year => {
      const option = document.createElement('option');
      option.value = year;
      option.textContent = year;
      yearSelect.appendChild(option);
    });

    yearSelect.addEventListener('change', (e) => {
      this.filters.year = e.target.value || null;
      this.renderMarkers();
    });

    // Similar for county, status filters...
  }
}

// Initialize on load
document.addEventListener('DOMContentLoaded', () => {
  const app = new MapApp();
  app.init();
});
```

## Google Sheets as database

### Fetching published CSV

```javascript
// Google Sheets published as CSV
const SHEET_URL = 'https://docs.google.com/spreadsheets/d/e/SPREADSHEET_ID/pub?gid=0&single=true&output=csv';

async function loadFromSheets() {
  const response = await fetch(SHEET_URL);
  const csv = await response.text();

  // Parse with PapaParse (CDN)
  const { data, errors } = Papa.parse(csv, {
    header: true,
    skipEmptyLines: true,
    transformHeader: (h) => h.trim().toLowerCase().replace(/\s+/g, '_')
  });

  if (errors.length > 0) {
    console.warn('CSV parsing errors:', errors);
  }

  return data;
}
```

### Real-time state with localStorage

```javascript
class DataManager {
  constructor(sheetUrl, cacheKey) {
    this.sheetUrl = sheetUrl;
    this.cacheKey = cacheKey;
    this.data = [];
    this.localState = this.loadLocalState();
  }

  loadLocalState() {
    const stored = localStorage.getItem(`${this.cacheKey}-state`);
    return stored ? JSON.parse(stored) : {};
  }

  saveLocalState() {
    localStorage.setItem(`${this.cacheKey}-state`, JSON.stringify(this.localState));
  }

  async refresh() {
    const response = await fetch(this.sheetUrl);
    const csv = await response.text();
    this.data = Papa.parse(csv, { header: true, skipEmptyLines: true }).data;

    // Merge with local state
    this.data.forEach(row => {
      const localData = this.localState[row.id];
      if (localData) {
        Object.assign(row, localData);
      }
    });

    return this.data;
  }

  updateLocal(id, updates) {
    this.localState[id] = { ...this.localState[id], ...updates };
    this.saveLocalState();

    // Update in-memory data too
    const item = this.data.find(d => d.id === id);
    if (item) Object.assign(item, updates);
  }
}

// Usage
const manager = new DataManager(SHEET_URL, 'volunteer-data');
await manager.refresh();

// Mark task as complete (stored locally)
manager.updateLocal('task-123', { completed: true, completed_at: new Date().toISOString() });
```

## Browser extension (Manifest V3)

### manifest.json

```json
{
  "manifest_version": 3,
  "name": "PocketLink",
  "version": "1.0.0",
  "description": "Create shortlinks from right-click context menu",

  "permissions": [
    "contextMenus",
    "storage",
    "activeTab",
    "scripting",
    "notifications",
    "offscreen"
  ],

  "background": {
    "service_worker": "background.js",
    "type": "module"
  },

  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },

  "options_page": "options.html",

  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}
```

### Service worker (background.js)

```javascript
// background.js - Service Worker

// Create context menu on install
chrome.runtime.onInstalled.addListener(() => {
  chrome.contextMenus.create({
    id: 'create-shortlink',
    title: 'Create Shortlink',
    contexts: ['page', 'link']
  });
});

// Handle context menu click
chrome.contextMenus.onClicked.addListener(async (info, tab) => {
  if (info.menuItemId !== 'create-shortlink') return;

  const url = info.linkUrl || info.pageUrl;

  try {
    const shortUrl = await createShortlink(url);
    await copyToClipboard(shortUrl);
    showNotification('Shortlink Created', shortUrl);
  } catch (error) {
    showNotification('Error', error.message);
  }
});

async function createShortlink(longUrl) {
  const { apiToken } = await chrome.storage.sync.get('apiToken');
  if (!apiToken) throw new Error('API token not configured');

  const response = await fetch('https://api-ssl.bitly.com/v4/shorten', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${apiToken}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ long_url: longUrl })
  });

  if (!response.ok) throw new Error('API request failed');

  const data = await response.json();
  return data.link;
}

// Clipboard methods (three fallback strategies)

// Method 1: Offscreen API (preferred)
async function copyToClipboard(text) {
  try {
    await copyViaOffscreen(text);
  } catch {
    try {
      await copyViaContentScript(text);
    } catch {
      await copyViaPopup(text);
    }
  }
}

async function copyViaOffscreen(text) {
  await chrome.offscreen.createDocument({
    url: 'offscreen.html',
    reasons: ['CLIPBOARD'],
    justification: 'Copy shortlink to clipboard'
  });

  await chrome.runtime.sendMessage({ type: 'copy', text });
  await chrome.offscreen.closeDocument();
}

async function copyViaContentScript(text) {
  const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
  await chrome.scripting.executeScript({
    target: { tabId: tab.id },
    func: (text) => navigator.clipboard.writeText(text),
    args: [text]
  });
}

function showNotification(title, message) {
  chrome.notifications.create({
    type: 'basic',
    iconUrl: 'icons/icon48.png',
    title,
    message
  });
}
```

### Options page

```html
<!-- options.html -->
<!DOCTYPE html>
<html>
<head>
  <style>
    /* Inline CSS for extension compliance (no remote code) */
    body {
      font-family: system-ui, sans-serif;
      padding: 20px;
      max-width: 400px;
      margin: 0 auto;
    }
    h1 { font-size: 1.5rem; margin-bottom: 1rem; }
    label { display: block; margin-bottom: 0.5rem; font-weight: 500; }
    input {
      width: 100%;
      padding: 8px;
      border: 1px solid #ccc;
      border-radius: 4px;
      font-size: 14px;
    }
    button {
      margin-top: 1rem;
      padding: 10px 20px;
      background: #2dc8d2;
      color: white;
      border: none;
      border-radius: 4px;
      cursor: pointer;
    }
    button:hover { background: #25a8b0; }
    .status { margin-top: 1rem; padding: 10px; border-radius: 4px; }
    .success { background: #d4edda; color: #155724; }
    .error { background: #f8d7da; color: #721c24; }
  </style>
</head>
<body>
  <h1>PocketLink Settings</h1>

  <label for="apiToken">Bit.ly API Token</label>
  <input type="password" id="apiToken" placeholder="Enter your API token">

  <button id="save">Save Settings</button>

  <div id="status" class="status" style="display: none;"></div>

  <script src="options.js"></script>
</body>
</html>
```

```javascript
// options.js
document.addEventListener('DOMContentLoaded', async () => {
  const tokenInput = document.getElementById('apiToken');
  const saveButton = document.getElementById('save');
  const status = document.getElementById('status');

  // Load saved token
  const { apiToken } = await chrome.storage.sync.get('apiToken');
  if (apiToken) tokenInput.value = apiToken;

  saveButton.addEventListener('click', async () => {
    const token = tokenInput.value.trim();

    if (!token) {
      showStatus('Please enter an API token', 'error');
      return;
    }

    // Validate token by making test request
    try {
      const response = await fetch('https://api-ssl.bitly.com/v4/user', {
        headers: { 'Authorization': `Bearer ${token}` }
      });

      if (!response.ok) throw new Error('Invalid token');

      await chrome.storage.sync.set({ apiToken: token });
      showStatus('Settings saved successfully!', 'success');
    } catch {
      showStatus('Invalid API token', 'error');
    }
  });

  function showStatus(message, type) {
    status.textContent = message;
    status.className = `status ${type}`;
    status.style.display = 'block';
    setTimeout(() => { status.style.display = 'none'; }, 3000);
  }
});
```

## Cache busting for deployments

```html
<!-- Manual versioning for static files -->
<link rel="stylesheet" href="styles.css?v=1.3.0">
<script src="app.js?v=1.3.0"></script>

<!-- Or use build timestamp -->
<script>
  const version = Date.now();
  document.write(`<link rel="stylesheet" href="styles.css?v=${version}">`);
</script>
```

## Deployment patterns

### Static hosting (FTP/SFTP)
```
# Directory structure for WordPress wp-content deployment
wp-content/
└── archive-explorer/
    ├── index.html
    ├── index.js
    ├── index.css
    ├── components/
    │   ├── Sidebar.js
    │   ├── RecordList.js
    │   └── RecordCard.js
    └── data/
        └── archive-data.json
```

### Path management for subdirectory deployment
```javascript
// constants.js

// Auto-detect base path from current URL
const getBasePath = () => {
  const path = window.location.pathname;
  const lastSlash = path.lastIndexOf('/');
  return path.substring(0, lastSlash + 1);
};

export const BASE_PATH = getBasePath();
export const DATA_URL = `${BASE_PATH}data/archive-data.json`;

// Usage
const response = await fetch(DATA_URL);
```

## Performance tips

- **Lazy load large JSON**: Parse incrementally or paginate
- **Use CSS containment**: `contain: layout style` on repeated elements
- **Debounce search input**: Wait 300ms after typing stops
- **Virtualize long lists**: Only render visible items
- **Preconnect to CDNs**: `<link rel="preconnect" href="https://esm.sh">`