Mongoose gives validation error even when required fields are present - node.js

Question

I'm using the mongoose ODM for a project. My schema looks like this:
const applicantSchema = new Schema({
regno: {
type: String,
unique: true,
required: true
},
email: {
type: String,
unique: true,
required: true
}
});
const Applicant = mongoose.model('Applicant', applicantSchema);
I created a wrapper function to add a new document which looks like this:
function addApplicant(newApplicant, callback){
mongoose.connect(url);
const db = mongoose.connection;
console.log(newApplicant);
console.log(typeof newApplicant);
const applicant = new Applicant(newApplicant);
applicant.save((err) => {
if(err) return callback(err);
let info = "successfully saved target";
return callback(null, info);
});
}
I call this function within my route that handles the concerned post request.
router.post('/applicant/response', (req, res) => {
//process sent response here and add to DB
//console.log(req.body);
let newApplicant = {
regno: req.body.regno,
email: req.body.email
}
//console.log(newApplicant);
applicant.addApplicant(newApplicant, (err, info) => {
if(err){ console.log(err); res.end(err);}
res.end('complete, resp: ' + info);
});
});
However, mongoose gives me a validation error (path 'regno' is required) even though I am supplying a value for regno. This happens with all the fields marked as required.
If I remove the 'required: true' option the document is saved to the db as expected.
Any help will be appreciated. :)

Answer 1

It turns out that in this case, something was wrong with the way postman was sending data in a POST request. When I tested this later in postman using JSON as the data format (and ensuring that the Content-Type header is set to application/json), the code worked as expected.
To those facing a similar issue, check the headers postman sends with the request, and ensure that they are what you'd expect them to be.

Answer 2

In your express entry file where you expose your endpoints and setup express you should have app.use(express.json()); written above the endpoint.
const express = require("express");
require("./src/db/mongoose");
const User = require("./src/models/user");
const app = express();
const port = process.env.PORT || 3000;
// THIS LINE IS MANDATORY
app.use(express.json());
app.post("/users", async(req, res) => {
const user = new User(req.body);
try {
await user.status(201).save();
res.send(user);
} catch (error) {
res.status(400).send(error);
}
});
app.listen(port, () => {
console.log(`Server is runnung in port ${port}`);
});