gatsbyjs and expressjs Error 400 Bad Request while fetch - node.js

Question

I have a small backend with ExpressJS that sends an email, I have deployed this backend on a Heroku site, I have tried it with postman and everything is ok, it works, but when I want to use it from my gatsby site, it throws a problem with cors, the gatsby site is running on my localhost.
ExpressJS code:
import dotenv from 'dotenv';
import express from 'express';
import nodemailer from 'nodemailer';
import cors from 'cors';
if (process.env.NODE_ENV !== 'production') {
dotenv.config();
}
const app = express();
app.use(express.urlencoded({ extended: true }));
app.use(cors());
const contactAddress = process.env.CONTACT_ADDRESS || '';
const mailer = nodemailer.createTransport({
service: 'Gmail',
auth: {
user: process.env.GMAIL_ADDRESS,
pass: process.env.GMAIL_PASSWORD,
},
});
app.post('/contact', (req, res) => {
if (!req.body.from)
return res.status(400).json({ message: 'From is required' });
if (!req.body.message)
return res.status(400).json({ message: 'Message is required' });
mailer.sendMail(
{
from: req.body.from,
to: [contactAddress],
subject: 'Contact from API',
html: `<h3>${req.body.from}</h3><br>${req.body.message}`,
},
(err, info) => {
if (err) {
console.log(err);
return res.status(500).send(err);
}
res.status(200).json({ success: true });
}
);
});
app.listen(process.env.PORT || 8000);
console.log(`App running on port ${process.env.PORT || 8000}`);
Code on frontend that make the request:
const onSubmit = async (data: IFormInputs) => {
console.log(data);
const formData = new FormData();
Object.keys(data).forEach((el) => {
formData.append(el, data[el]);
});
try {
const res = await fetch(`${BACKEND_URL}contact`, {
method: 'POST',
body: formData,
});
console.log(res);
} catch (e) {
console.log(e);
}
}
I have also tried adding some configuration on the fetch, but it does not work anyways
const res = await fetch(`${BACKEND_URL}contact`, {
method: 'POST',
mode: 'cors',
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
'Accept': 'application/json',
},
referrerPolicy: 'origin',
body: formData,
});
The error throws the following error:
{
status: 400,
statusText: "Bad Request",
type: "cors",
ok: false,
}
I have searched similar questions on StackOverflow, but any of the solutions have worked for me.
The answer on this post does not work for me, because I don't have the backend and the frontend on localhost, I am consuming the API from my Heroku site.
Thanks in advance!

Answer 1

You are listening on the port 8000. Are you sure it's correct? Let's try on posts 8080.
You can also set headers:
app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", '*');
res.header("Access-Control-Allow-Credentials", true);
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
res.header("Access-Control-Allow-Headers", 'Origin,X-Requested-With,Content-Type,Accept,content-type,application/json');
next();
});