Implement P2P polling app with Yjs and WebRTC

Uses Yjs CRDTs for conflict-free shared state and y-webrtc for peer-to-peer data exchange. Users can add poll options and vote/unvote, with all changes syncing in real-time across connected peers. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-15 04:32:06 +01:00
7 changed files with 1769 additions and 207 deletions
--- a/PollingApp.html
+++ b/PollingApp.html
@@ -1,200 +0,0 @@
 <!DOCTYPE html>
 <html lang="en">
 <head>
 <meta charset="UTF-8">
 <title>Peer‑to‑Peer Poll – up to 14 users (no vote loops)</title>
 <style>
  body {font-family:Arial,Helvetica,sans-serif; margin:20px;}
  #options li {margin:5px 0;}
  button {margin-left:5px;}
 </style>
 </head>
 <body>
 <h2>Peer‑to‑Peer Poll (max 14 participants)</h2>
 <div id="setup">
  <label>Your Peer ID: <input id="myId" readonly size="30"></label><br><br>
  <label>Room host ID (leave empty if you are the first client):
    <input id="hostId" placeholder="host peer id">
  </label>
  <button id="joinBtn">Join / Create Room</button>
  <p id="status"></p>
 </div>
 <hr>
 <h3>Poll</h3>
 <ul id="options"></ul>
 <input id="newOption" placeholder="New option text">
 <button id="addOptionBtn">Add option</button>
 <script src="https://unpkg.com/peerjs@1.5.4/dist/peerjs.min.js"></script>
 <script>
 /* ---------- 1. Initialise PeerJS ---------- */
 const peer = new Peer();                     // public signalling server
 const myIdInput = document.getElementById('myId');
 const statusEl   = document.getElementById('status');
 let isHost = false;                          // true for the first client
 let connections = [];                        // all open DataConnections
 let knownPeers = new Set();                  // IDs of every peer we know (including host)
 peer.on('open', id => {
  myIdInput.value = id;
  statusEl.textContent = 'Enter a host ID (or leave empty) and click Join.';
 });
 /* ---------- 2. Accept incoming connections (host side) ---------- */
 peer.on('connection', incoming => {
  registerConnection(incoming);
 });
 /* ---------- 3. Join / create a room ---------- */
 document.getElementById('joinBtn').onclick = () => {
  const hostId = document.getElementById('hostId').value.trim();
  if (hostId) {
    isHost = false;
    connectToPeer(hostId);
    statusEl.textContent = `Connecting to host ${hostId}…`;
  } else {
    isHost = true;
    knownPeers.add(peer.id);
    statusEl.textContent = 'Room created – share this Peer ID with others.';
  }
 };
 /* ---------- 4. Helper: connect to a remote peer ---------- */
 function connectToPeer(peerId) {
  if (knownPeers.has(peerId)) return;
  const conn = peer.connect(peerId);
  registerConnection(conn);
 }
 /* ---------- 5. Register a DataConnection ---------- */
 function registerConnection(conn) {
  if (!conn) return;
  connections.push(conn);
  knownPeers.add(conn.peer);
  conn.on('open', () => {
    // 1️⃣ Send full poll state
    conn.send({type: 'full', payload: poll, msgId: crypto.randomUUID()});
    // 2️⃣ If we are the host, tell the newcomer about other peers
    if (isHost) {
      const others = Array.from(knownPeers).filter(id => id !== conn.peer && id !== peer.id);
      if (others.length) conn.send({type: 'peer-list', payload: others, msgId: crypto.randomUUID()});
    }
  });
  conn.on('data', data => handleMessage(data, conn.peer));
  conn.on('close', () => {
    connections = connections.filter(c => c !== conn);
    knownPeers.delete(conn.peer);
  });
 }
 /* ---------- 6. Shared poll state ---------- */
 let poll = {options: []};   // each option: {id, text, votes}
 /* ---------- 7. Track my own votes ---------- */
 const myVotes = new Set();   // option.id values
 /* ---------- 8. Remember which messages we already processed ---------- */
 const seenMsgIds = new Set();
 /* ---------- 9. Broadcast helper (skip the sender) ---------- */
 function broadcast(msg, except = null) {
  connections.forEach(c => {
    if (c.open && c.peer !== except) c.send(msg);
  });
 }
 /* ---------- 10. Message handling ---------- */
 function handleMessage(msg, senderId) {
  // Ignore duplicates
  if (seenMsgIds.has(msg.msgId)) return;
  seenMsgIds.add(msg.msgId);
  switch (msg.type) {
    case 'full':
      poll = msg.payload;
      render();
      break;
    case 'add':
      poll.options.push(msg.payload);
      render();
      broadcast(msg, senderId);   // forward once
      break;
    case 'vote':
      const opt = poll.options.find(o => o.id === msg.payload.id);
      if (opt) opt.votes++;
      render();
      broadcast(msg, senderId);
      break;
    case 'peer-list':
      msg.payload.forEach(id => {
        if (id !== peer.id && !knownPeers.has(id)) connectToPeer(id);
      });
      break;
  }
 }
 /* ---------- 11. UI rendering ---------- */
 function render() {
  const ul = document.getElementById('options');
  ul.innerHTML = '';
  poll.options.forEach(opt => {
    const li = document.createElement('li');
    li.textContent = `${opt.text} – ${opt.votes} vote(s)`;
    const btn = document.createElement('button');
    btn.textContent = myVotes.has(opt.id) ? 'Voted' : 'Vote';
    btn.disabled = myVotes.has(opt.id);
    btn.onclick = () => {
      // Record locally – prevents double‑click on the same client
      myVotes.add(opt.id);
      btn.textContent = 'Voted';
      btn.disabled = true;
      const voteMsg = {
        type: 'vote',
        payload: {id: opt.id},
        msgId: crypto.randomUUID()
      };
      // Apply locally first
      opt.votes++;
      render();
      // Send to all peers
      broadcast(voteMsg);
    };
    li.appendChild(btn);
    ul.appendChild(li);
  });
 }
 /* ---------- 12. Add new option ---------- */
 document.getElementById('addOptionBtn').onclick = () => {
  const txt = document.getElementById('newOption').value.trim();
  if (!txt) return;
  const option = {id: crypto.randomUUID(), text: txt, votes: 0};
  poll.options.push(option);
  render();
  const addMsg = {
    type: 'add',
    payload: option,
    msgId: crypto.randomUUID()
  };
  broadcast(addMsg);
  document.getElementById('newOption').value = '';
 };
 </script>
 </body>
 </html>
--- a/README.md
+++ b/README.md
@@ -1,7 +1 @@
 # P2P Poll App
 This is a very simple polling app using peerjs.
 It runs as a single HTML file and can handle multiple users in one poll room.
 The app once open is self explanatory.
 App created with the help of GPTOSS120B.
--- a/index.html
+++ b/index.html
@@ -0,0 +1,33 @@
 <!DOCTYPE html>
 <html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>P2P Poll</title>
  <link rel="stylesheet" href="/src/style.css">
 </head>
 <body>
  <div id="app">
    <header>
      <h1>P2P Poll</h1>
      <div id="status">
        <span id="connection-status" class="connecting">Connecting...</span>
        <span id="peer-count">1 peer</span>
      </div>
    </header>
    <main>
      <div id="add-option">
        <input type="text" id="option-input" placeholder="Add a poll option..." maxlength="100">
        <button id="add-btn">Add</button>
      </div>
      <div id="poll-options"></div>
      <p id="empty-state">No options yet. Add one above!</p>
    </main>
  </div>
  <script type="module" src="/src/main.js"></script>
 </body>
 </html>
--- a/package-lock.json
+++ b/package-lock.json
--- a/package.json
+++ b/package.json
@@ -0,0 +1,18 @@
 {
  "name": "p2p-poll",
  "private": true,
  "version": "1.0.0",
  "type": "module",
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "preview": "vite preview"
  },
  "dependencies": {
    "yjs": "^13.6.0",
    "y-webrtc": "^10.3.0"
  },
  "devDependencies": {
    "vite": "^6.0.0"
  }
 }
--- a/src/main.js
+++ b/src/main.js
@@ -0,0 +1,136 @@
 import * as Y from 'yjs';
 import { WebrtcProvider } from 'y-webrtc';
 // --- Peer ID (stable across reloads) ---
 function getOrCreatePeerId() {
  let id = localStorage.getItem('peer-id');
  if (!id) {
    id = crypto.randomUUID();
    localStorage.setItem('peer-id', id);
  }
  return id;
 }
 const peerId = getOrCreatePeerId();
 // --- Room name from URL ---
 function getRoomName() {
  const params = new URLSearchParams(window.location.search);
  return params.get('room') || 'default-poll';
 }
 const roomName = getRoomName();
 // --- Yjs setup ---
 const ydoc = new Y.Doc();
 const provider = new WebrtcProvider(roomName, ydoc);
 const yOptions = ydoc.getMap('poll-options');
 // --- Data operations ---
 function addOption(name) {
  const id = crypto.randomUUID();
  const optionMap = new Y.Map();
  optionMap.set('name', name);
  optionMap.set('votes', new Y.Map());
  yOptions.set(id, optionMap);
 }
 function toggleVote(optionId) {
  const optionMap = yOptions.get(optionId);
  if (!optionMap) return;
  const votes = optionMap.get('votes');
  if (votes.has(peerId)) {
    votes.delete(peerId);
  } else {
    votes.set(peerId, true);
  }
 }
 // --- UI rendering ---
 const container = document.getElementById('poll-options');
 const emptyState = document.getElementById('empty-state');
 function render() {
  container.innerHTML = '';
  const entries = [];
  yOptions.forEach((optionMap, id) => {
    entries.push({
      id,
      name: optionMap.get('name'),
      votes: optionMap.get('votes').size,
      voted: optionMap.get('votes').has(peerId),
    });
  });
  entries.sort((a, b) => b.votes - a.votes || a.name.localeCompare(b.name));
  emptyState.className = entries.length > 0 ? 'hidden' : '';
  for (const entry of entries) {
    const div = document.createElement('div');
    div.className = 'poll-option';
    const nameSpan = document.createElement('span');
    nameSpan.className = 'option-name';
    nameSpan.textContent = entry.name;
    const voteCount = document.createElement('span');
    voteCount.className = 'vote-count';
    voteCount.textContent = entry.votes;
    const voteBtn = document.createElement('button');
    voteBtn.className = entry.voted ? 'vote-btn voted' : 'vote-btn';
    voteBtn.textContent = entry.voted ? 'Unvote' : 'Vote';
    voteBtn.addEventListener('click', () => toggleVote(entry.id));
    div.append(nameSpan, voteCount, voteBtn);
    container.appendChild(div);
  }
 }
 // Re-render on any change in the shared state
 yOptions.observeDeep(() => render());
 // --- Add option handlers ---
 const input = document.getElementById('option-input');
 const addBtn = document.getElementById('add-btn');
 addBtn.addEventListener('click', () => {
  const name = input.value.trim();
  if (name) {
    addOption(name);
    input.value = '';
  }
 });
 input.addEventListener('keydown', (e) => {
  if (e.key === 'Enter') addBtn.click();
 });
 // --- Connection status & peer count ---
 const statusEl = document.getElementById('connection-status');
 const peerCountEl = document.getElementById('peer-count');
 provider.on('synced', ({ synced }) => {
  statusEl.textContent = synced ? 'Connected' : 'Connecting...';
  statusEl.className = synced ? 'connected' : 'connecting';
 });
 function updatePeerCount() {
  const count = provider.awareness.getStates().size;
  peerCountEl.textContent = `${count} peer${count !== 1 ? 's' : ''}`;
 }
 provider.awareness.on('change', updatePeerCount);
 updatePeerCount();
 // --- Initial render ---
 render();
--- a/src/style.css
+++ b/src/style.css
@@ -0,0 +1,144 @@
 * {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
 }
 body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #f5f5f5;
  color: #333;
  min-height: 100vh;
 }
 #app {
  max-width: 600px;
  margin: 0 auto;
  padding: 2rem 1rem;
 }
 header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
 }
 h1 {
  font-size: 1.5rem;
 }
 #status {
  display: flex;
  gap: 1rem;
  font-size: 0.85rem;
  color: #666;
 }
 #connection-status::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-right: 4px;
  vertical-align: middle;
 }
 #connection-status.connected::before {
  background: #4caf50;
 }
 #connection-status.connecting::before {
  background: #ff9800;
 }
 #add-option {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
 }
 #option-input {
  flex: 1;
  padding: 0.6rem 0.8rem;
  border: 1px solid #ddd;
  border-radius: 6px;
  font-size: 1rem;
  outline: none;
 }
 #option-input:focus {
  border-color: #2196f3;
 }
 #add-btn {
  padding: 0.6rem 1.2rem;
  background: #2196f3;
  color: white;
  border: none;
  border-radius: 6px;
  font-size: 1rem;
  cursor: pointer;
 }
 #add-btn:hover {
  background: #1976d2;
 }
 .poll-option {
  display: flex;
  align-items: center;
  background: white;
  padding: 0.8rem 1rem;
  border-radius: 8px;
  margin-bottom: 0.5rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
 }
 .option-name {
  flex: 1;
  font-size: 1rem;
 }
 .vote-count {
  font-size: 0.9rem;
  font-weight: 600;
  color: #666;
  margin-right: 0.75rem;
  min-width: 1.5rem;
  text-align: center;
 }
 .vote-btn {
  padding: 0.4rem 1rem;
  border: 2px solid #2196f3;
  border-radius: 6px;
  font-size: 0.85rem;
  cursor: pointer;
  background: white;
  color: #2196f3;
 }
 .vote-btn:hover {
  background: #e3f2fd;
 }
 .vote-btn.voted {
  background: #2196f3;
  color: white;
 }
 .vote-btn.voted:hover {
  background: #1976d2;
 }
 #empty-state {
  text-align: center;
  color: #999;
  padding: 2rem;
 }
 #empty-state.hidden {
  display: none;
 }