keeps getting "Illegal arguments: undefined, string at Object.bcrypt.hashSync" - node.js

Question

I've been struggling with Bcrypt on my MERN project I'm trying to create an authentication system I'm trying to run tests on Postman and I'm not sure why do I keep getting the error: "Illegal arguments: undefined, string at Object.bcrypt.hashSync"
this is my postman request:
this is the Controller Code:
const config = require("../config/auth.config");
const db = require("../models");
const User = db.user;
const Role = db.role;
var jwt = require("jsonwebtoken");
var bcrypt = require("bcryptjs");
exports.signup = (req, res) => {
const user = new User({
username: req.body.username,
email: req.body.email,
password: bcrypt.hashSync(req.body.password, 8),
});
user.save((err, user) => {
if (err) {
res.status(500).send({ message: err });
return;
}
if (req.body.roles) {
Role.find(
{
name: { $in: req.body.roles },
},
(err, roles) => {
if (err) {
res.status(500).send({ message: err });
return;
}
user.roles = roles.map((role) => role._id);
user.save((err) => {
if (err) {
res.status(500).send({ message: err });
return;
}
res.send({ message: "User was registered successfully!" });
});
}
);
} else {
Role.findOne({ name: "user" }, (err, role) => {
if (err) {
res.status(500).send({ message: err });
return;
}
user.roles = [role._id];
user.save((err) => {
if (err) {
res.status(500).send({ message: err });
return;
}
res.send({ message: "User was registered successfully!" });
});
});
}
});
};
exports.signin = (req, res) => {
User.findOne({
username: req.body.username,
})
.populate("roles", "-__v")
.exec((err, user) => {
if (err) {
res.status(500).send({ message: err });
return;
}
if (!user) {
return res.status(404).send({ message: "User Not found." });
}
var passwordIsValid = bcrypt.compareSync(
req.body.password,
user.password
);
if (!passwordIsValid) {
return res.status(401).send({ message: "Invalid Password!" });
}
var token = jwt.sign({ id: user.id }, config.secret, {
expiresIn: 86400, // 24 hours
});
var authorities = [];
for (let i = 0; i < user.roles.length; i++) {
authorities.push("ROLE_" + user.roles[i].name.toUpperCase());
}
req.session.token = token;
res.status(200).send({
id: user._id,
username: user.username,
email: user.email,
roles: authorities,
});
});
};
exports.signout = async (req, res) => {
try {
req.session = null;
return res.status(200).send({ message: "You've been signed out!" });
} catch (err) {
this.next(err);
}
};

Answer 1

The error message:
Illegal arguments: undefined, string at Object.bcrypt.hashSync wants to say that you're passing undefined as an argument to the hashSync function. We need to fix this error.
Take a closer look at this line where the error occurs:
password: bcrypt.hashSync(req.body.password, 8),
req.body.password is undefined, you can verify it by console.log(req.body.password). What's wrong is that you are sending data as URL parameters. So req.body is an empty object and req.body.password is undefined.
In Postman, select the Body tab, choose JSON format, then type your data as a JSON object. Then, in your code, use express.json() middleware to parse requests in JSON format. You'll have the desired output.
You can see my example request in Postman below: