JSON Parse error: Unexpected identifier "Not found" - node.js

Question

fetch('http://192.168.120.100:8080/login', {
method: 'POST',
body: JSON.stringify(SignInData),
headers: {
'Content-Type': 'application/json'
}
})
.then((response)=>response.json())
.then((user)=>{
if(user.status=="success"){
alert("success")
console.log("success");
}else{
alert("error")
console.log("fail");
}
})
.catch((error)=>{
console.log("Error, with message::",error)
});
}
and my server code is
router.post('/login', function (req, res) {
User.findOne({ email: req.body.email }).then((user) => {
console.log('testing' + JSON.stringify(user));
if (!user) return res.status(404).send("Not found");
//check password matches
if (user.password == req.body.password) {
user.status = "Success";
res.status(200).send('success');
} else {
res.status(404).send('Invalid Password');
}
})
.catch((err) => {
res.status(500).send(err);
});
});
});
i am working on signin form and my backend is working fine but while running on react native i am getting an error JSON Parse error: Unexpected identifier "Not".is it a json error ?

Answer 1

Looks like the problem is when you are passing the "Not found" in the case user not found , well for that matter even 'success'
On the UI side when you call .then((response)=>response.json()) It tries to change the response to a json format, whereas your API is returning String "Not Found" which does not conform to json structure.
as for solution you can pass JSON in all scenarios, you might need to change your UI accordingly.
router.post('/login', function (req, res) {
User.findOne({ email: req.body.email }).then((user) => {
console.log('testing' + JSON.stringify(user));
var result = {};
if (!user) {
result.message = "Not Found"
return res.status(404).send(result);
}
//check password matches
if (user.password == req.body.password) {
user.status = "Success";
result.message = "Success"
res.status(200).send(user);
} else {
result.message = "Invalid Password";
res.status(404).send(result);
}
})
.catch((err) => {
res.status(500).send(err);
});
});
});