Node js Error Handling it crash the server - node.js

Question

Error handling in NODE JS
this is my Login Function
router.post('/admin/login', function (req, res) {
User.findOne({ username: req.body.username }, function (err, user) {
if (err) return res.status(500).send('Error on the server.');
if (!user) return res.status(404).send('No user found.');
var passwordIsValid = bcrypt.compareSync(req.body.password, user.password);
if (!passwordIsValid) return res.status(401).send({ auth: false, token: null });
if (req.body.username && req.body.password) {
console.log("enter");
var token = jwt.sign({ id: user._id }, config.secret, {
expiresIn: 86400 // expires in 24 hours
});
res.status(200).send({ auth: true, token: token });
} else {
return res.status(500).send('Error on the server.');
//res.status(500).send("Check Username & Password");
}
});
});
if i forget to enter password the server will be crashed how to handle on this

Answer 1

You need to check to see if the password is being passed before you pass it into the compareSync function.
if (!req.body.password) {
// handle error
return res.status(401).send("Missing or invalid password")
}
If you're doing this you should also check if req.body.username is being provided in the post request. Alternatively for easier method, you can have a try catch wrapped around the query to handle other unexpected errors.

Answer 2

It's better to check in front-end (client side) and also to check for email and password in back-end , there is various libraries to do that , for example i use express-validator lib here is a simple check and of course you can read full docs https://express-validator.github.io/docs/
code sample :
const { check, validationResult, body } = require('express-validator/check');
router.post('/admin/login',[check('email').isEmail(),check('password').isLength({ min: 5 })], (req, res) => {
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(422).json({ errors: errors.array() });
}
// the rest of your sing in code here
})
and you can check for name length also this is safer for your back-end always check for validation in front-end and back-end, never trust client side only , do your own validation in the back-end , i hope this answer your question

Answer 3

I was having the same issue with a very similar code.
I replaced this line:
(...)
if (!user) return res.status(404).send('No user found.');
For this:
User.findOne({username : req.body.username},function(err, user){
if(err){
return res.status(401).json({message : err})
};
/* Trying to repair error when username is not on DB */
if(user === null) {
return res.status(401).json({auth : false, token : null, message : "Not Authorised User"});
};
/* Replacement worked */
var isPasswordValid = bcrypt.compareSync(req.body.password, user.password);
Hope it works for you.