Stripe Payment Processing

Setup

import Stripe from 'stripe';
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);

Checkout Session (simplest integration)

app.post('/api/checkout', async (req, res) => {
  const session = await stripe.checkout.sessions.create({
    mode: 'payment', // or 'subscription'
    line_items: [{ price: req.body.priceId, quantity: 1 }],
    success_url: `${process.env.APP_URL}/success?session_id={CHECKOUT_SESSION_ID}`,
    cancel_url: `${process.env.APP_URL}/cancel`,
    metadata: { userId: req.user.id },
  });
  res.json({ url: session.url });
});

Payment Intents (custom UI)

// Server: create intent
app.post('/api/payment-intent', async (req, res) => {
  const intent = await stripe.paymentIntents.create({
    amount: Math.round(req.body.amount * 100), // cents
    currency: 'usd',
    automatic_payment_methods: { enabled: true },
    metadata: { orderId: req.body.orderId },
  }, { idempotencyKey: `order_${req.body.orderId}` });
  res.json({ clientSecret: intent.client_secret });
});

// Client: React + Stripe.js
import { useStripe, useElements, PaymentElement } from '@stripe/react-stripe-js';

function CheckoutForm() {
  const stripe = useStripe();
  const elements = useElements();

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    const { error } = await stripe!.confirmPayment({
      elements: elements!,
      confirmParams: { return_url: `${window.location.origin}/success` },
    });
    if (error) setError(error.message!);
  };

  return (
    <form onSubmit={handleSubmit}>
      <PaymentElement />
      <button disabled={!stripe}>Pay</button>
    </form>
  );
}

Subscriptions

app.post('/api/subscribe', async (req, res) => {
  const subscription = await stripe.subscriptions.create({
    customer: customerId,
    items: [{ price: req.body.priceId }],
    payment_behavior: 'default_incomplete',
    expand: ['latest_invoice.payment_intent'],
  });
  const invoice = subscription.latest_invoice as Stripe.Invoice;
  const pi = invoice.payment_intent as Stripe.PaymentIntent;
  res.json({ subscriptionId: subscription.id, clientSecret: pi.client_secret });
});

// Cancel at period end (not immediately)
await stripe.subscriptions.update(subId, { cancel_at_period_end: true });

Webhooks (critical)

app.post('/webhooks/stripe', express.raw({ type: 'application/json' }), (req, res) => {
  const event = stripe.webhooks.constructEvent(
    req.body, req.headers['stripe-signature']!, process.env.STRIPE_WEBHOOK_SECRET!
  );

  switch (event.type) {
    case 'checkout.session.completed':
      await fulfillOrder(event.data.object as Stripe.Checkout.Session);
      break;
    case 'invoice.paid':
      await activateSubscription(event.data.object as Stripe.Invoice);
      break;
    case 'invoice.payment_failed':
      await handleFailedPayment(event.data.object as Stripe.Invoice);
      break;
    case 'customer.subscription.deleted':
      await deactivateSubscription(event.data.object as Stripe.Subscription);
      break;
  }
  res.json({ received: true });
});

Critical: Use express.raw() — parsed body breaks signature verification.

Anti-Patterns

Quick Troubleshooting

Production Checklist

• Webhook endpoint registered and verified
• Idempotency keys on all creates
• Amount calculated server-side
• Test mode for dev/staging, live for prod
• PCI compliance (never handle raw card data)
• Customer portal for subscription management
• Refund flow implemented