Although I'm not a backend developer, I do have experience with express and NodeJS. However, my current project involving MongoDB has hit a roadblock that I can't seem to resolve. Despite researching similar questions and answers, none of the solutions have helped me so far.
The error I'm facing typically arises when multiple responses are sent to the client for a single request. Below is the code snippet causing the problem:
app.post('/myapitest', (req, res) => {
switch (req.headers['type']) {
case MY_TYPE.A:
const connection_string = 'My MongoDB instance link;
if (connection_string) {
mongoose.connect(connection_string as string);
mongoose.connection.once('connected', () => {
mongoose.connection.db.listCollections().toArray().then((collections) => {
mongoose.connection.close(() => {
return res.status(200).json(collections);
});
}).catch((err) => {
mongoose.connection.close(() => {
return res.status(400).json({ error: err.message, message: 'looks like something is wrong with connecting to the mongodb' });
});
});
})
} else {
return res.status(401).send('POST request failed because connection_string is missing in headers or invalid.');
}
break;
default:
res.status(400).send('POST request failed because type is missing in headers or not supported.');
break;
}
Despite there being no issue of sending multiple responses in my code, I encounter the [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client error when testing from Postman. The initial request yields the expected response from MongoDB. However, upon sending another request without stopping the program, the error occurs.