There are two main ways for an application to communicate with another. The first is polling, which is like knocking on the application’s door every 10 minutes to see if it is home.

The second option is webhooks. A scenario you can imagine would be if the application were to send you a text message alerting you it has arrived home.

My Use Case

In the case of Stripe, I needed it to tell me when a purchase was made so that I could add certain data to my database.

I needed this to happen after the payment was processed by Stripe.

With a webhook, you can specify what type of event you want to listen for. So in my case it was payment_intent.succeeded.

After that event was triggered, Stripe will call the webhook endpoint that you specify in the Stripe Dashboard.

Your webhook endpoint, which you define in the Stripe interface, must reply to Stripe with a response status of 200, so that Stripe knows to stop hitting the endpoint.

If you don't do this, after five or so tries, Stripe will email you telling you the endpoint failed.

Here is an example endpoint:

app.post(
  '/webhook',
  bodyParser.raw({ type: 'application/json' }),
  (request, response) => {
    let event

    try {
      event = JSON.parse(request.body)
    } catch (err) {
      response.status(400).send(`Webhook Error: ${err.message}`)
    }

    // Handle the event
    if (event.type === 'payment_intent.succeeded') {
      const paymentIntent = event.data.object
      // Then define and call a method to handle the successful payment intent.
      // handlePaymentIntentSucceeded(paymentIntent);
      response.json({ received: true })
    } else {
      return response.status(400).end()
    }
    // Return a response to acknowledge receipt of the event
)

If Stripe does not receive a response it will eventually notify you in the Dashboard.

To test your webhook endpoint locally, you will need to install the stripe-cli.

I’m on a Mac, so I used Homebrew to install it.

Here is the code for that:

brew install stripe/stripe-cli/stripe
stripe login

You are going to want to open two terminal tabs. In one run:

stripe listen --forward-to localhost:5000/webhook

In another run:

stripe trigger payment_intent.succeeded

You should see that your endpoint is called!