Paddle を接続し、売上を訪問に紐づける

// Where you open the checkout (Paddle.js, after Paddle.Initialize).
const visitorId = (document.cookie.match(/(?:^|; )_tally_vid=([\w-]+)/) || [])[1];
Paddle.Checkout.open({
  items: [{ priceId: 'pri_123', quantity: 1 }],
  // customData needs at least one key, so it is left out without a visitor id.
  ...(visitorId ? { customData: { 'tally_visitor_id': visitorId } } : {}),
});

// Express with cookie-parser: a transaction your server creates for the checkout.
app.post('/checkout', async (req, res) => {
  const visitorId = req.cookies['_tally_vid'];
  const response = await fetch('https://api.paddle.com/transactions', {
    method: 'POST',
    headers: {
      Authorization: 'Bearer ' + process.env.PADDLE_API_KEY,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      items: [{ price_id: 'pri_123', quantity: 1 }],
      custom_data: visitorId ? { 'tally_visitor_id': visitorId } : null,
    }),
  });
  const { data } = await response.json();
  // On the page: Paddle.Checkout.open({ transactionId: data.id }).
  res.json({ transactionId: data.id });
});