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Author SHA1 Message Date
Patrick Charrier
e30de01c86 Improve README with usage instructions and tech overview
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-15 04:56:40 +01:00
Patrick Charrier
2490a267ee Restore original README
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-15 04:55:52 +01:00
Patrick Charrier
2af5da59c4 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 04:55:11 +01:00
Patrick Charrier
4a208ba05b feat: add comment 2026-03-10 03:11:54 +01:00
7 changed files with 1805 additions and 204 deletions

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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>PeertoPeer 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>PeertoPeer Poll (max14 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', () => {
// 1⃣ Send full poll state
conn.send({type: 'full', payload: poll, msgId: crypto.randomUUID()});
// 2⃣ 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 doubleclick 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>

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# 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 peer-to-peer polling app where users can add options and vote on them. All data syncs directly between browsers using WebRTC — no central server stores any poll data.
## How It Works
- **Yjs CRDTs** handle shared state — concurrent edits from different peers merge automatically without conflicts
- **y-webrtc** establishes direct WebRTC connections between browsers (a public signaling server is used only for peer discovery)
- Each user gets a stable random ID (stored in localStorage) ensuring one vote per user per option
- Polls are identified by room name, shareable via URL
## Getting Started
```bash
npm install
npm run dev
```
Open `http://localhost:5173` in your browser. To share a specific poll, use the `?room=` query parameter:
```
http://localhost:5173/?room=my-poll
```
Share this URL with others to join the same poll.
## Cross-Device Testing
```bash
npm run dev -- --host
```
Then open `http://<your-local-ip>:5173/?room=test` on another device on the same network.
## Tech Stack
- [Yjs](https://yjs.dev/) — CRDT library for conflict-free shared state
- [y-webrtc](https://github.com/yjs/y-webrtc) — WebRTC provider for P2P connectivity
- [Vite](https://vite.dev/) — Dev server and bundler
- Vanilla JS — No framework dependencies

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index.html Normal file
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<!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>

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package.json Normal file
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{
"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"
}
}

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src/main.js Normal file
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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();

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* {
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;
}