node.js modify response and store request at the same time - node.js

Question

So what I'm trying to do is to manualy overwrite response when there is a request to my json-server. I'm fine with that, but I dont know how to add a bit to also store the original request in database.
Here is my code (i'm sending as response the name from request and static uuid)
The next(); in if step is failing complaining it cannot setup headers.
module.exports = (req, res, next) => {
if (req.path == "/business") {
res.status(201);
res.jsonp({
id: "a23e1b13-cf69-461c-aa8a-a0eb99e41350",
name: req.body['name'],
revision: "1"
});
next();
}
else {
next();
}
}

Answer 1

If you want to pass data from middleware to any routes you can assign value with req object rather than res object.
app.use(function(req.res)) {
req.custom_data = {
id: "a23e1b13-cf69-461c-aa8a-a0eb99e41350",
name: req.body['name'],
revision: "1"
};
next();
}
From other location you can do like this.
module.exports = (req, res, next) => {
res.jsonp(req.custom_data)//something like this
}
It might help you.

Answer 2

You are right.
For example, we cannot:
server.js
const jsonServer = require("json-server")
const server = jsonServer.create()
const router = jsonServer.router("db.json")
server.use(jsonServer.defaults())
server.use(jsonServer.bodyParser)
server.use((req, res, next) => {
if (req.method === "POST" && req.url === "/business") {
res.status(201)
res.jsonp({
id: "a23e1b13-cf69-461c-aa8a-a0eb99e41350",
name: req.body["name"],
revision: "1"
})
}
next()
})
server.use(router)
server.listen(3000, () => {
console.log("JSON Server is running")
})
Or we get: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client when we run node server.js, because we have already set and sent the headers when we call res.jsonp, so we cannot do this again by calling server.use(router).
We have a couple options.
Option 1.
server.js
const jsonServer = require("json-server")
const server = jsonServer.create()
const router = jsonServer.router("db.json")
server.use(jsonServer.defaults())
server.use(router)
server.listen(3000, () => {
console.log("JSON Server is running")
})
db.json
{
"business": []
}
Now we can POST to our http://localhost:3000/business endpoint and save our request body to our database. However, we cannot amend the 201 status, nor the request body to something else.
Option 2.
server.js
const jsonServer = require("json-server")
const server = jsonServer.create()
server.use(jsonServer.defaults())
server.use(jsonServer.bodyParser)
server.post("/business", (req, res, next) => {
res.status(201)
res.jsonp({
id: "a23e1b13-cf69-461c-aa8a-a0eb99e41350",
name: req.body["name"],
revision: "1"
})
next()
})
server.listen(3000, () => {
console.log("JSON Server is running")
})
Now we get the correct response, but we can no longer save to our database business key, because we are calling server.post("/business"...
You could however use this in your own code and save it somewhere else (or write to your own database), as this response will be returned from a Promise.