Sending an error to client as callback of HTTP request

Question

I’m trying to implement a payment system in my app by running a separate server to handle payments with braintree. What I can’t figure out is how do I send an error to my client (when the payment went wrong) to handle the result client side. How can I force my client to go in the catch instead of then based on result.success ? Or how do I get the result.success in my .then ? Actually my result object has no property containing my result.success (result.success is a boolean)

Server:

router.post("/checkout", function (req, res) {
  var nonceFromTheClient = req.body.payment_method_nonce;
  var amount = req.body.amount;

  gateway.transaction.sale({
      amount: amount,
      paymentMethodNonce: nonceFromTheClient,
  }, function (err, result) {
      res.send(result.success);
      console.log("purchase result: " + result.success);
  });
});

Client :

fetch('https://test.herokuapp.com/checkout', {
    method: "POST",
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ payment_method_nonce: nonce, amount: this.props.amount })
  }).then((result) => {
    console.log(result);
  }).catch(() => {
    alert("error");
  });
}

Answer 1

Assuming that you are using express, you can send the response with a status code(in this case an error) like this:

    router.post("/checkout", function (req, res) {
    var nonceFromTheClient = req.body.payment_method_nonce;
    var amount = req.body.amount;

    gateway.transaction.sale({
        amount: amount,
        paymentMethodNonce: nonceFromTheClient,
    }, function (err, result) {
        if(err){
            res.status(401).send(err); //could be, 400, 401, 403, 404 etc. Depending of the error
        }else{
            res.status(200).send(result.success);
        }
    });
});

And in your client

fetch('https://test.herokuapp.com/checkout', {
    method: "POST",
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ payment_method_nonce: nonce, amount: this.props.amount })
}).then((result) => {
    console.log(result);
}).catch((error) => {
    console.log(error);
});