Files
427e7578-d7bf-49c8-aee9-2dd…/src/main.js
Patrick Charrier a621cc4483 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

137 lines
3.4 KiB
JavaScript

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();