Json at position error - node.js

Question

I am using passport.js for my backend (node.js) app to signin up the user. I am getting always following error:
ERROR SyntaxError: Unexpected token < in JSON at position 0
at Object.parse ()
at Response.webpackJsonp.../../../http/#angular/http.es5.js.Body.json
(http.es5.js:797)
at MapSubscriber.project (signup.component.ts:31)
After refresh the site I am signed-up. What is wrong with my code?
Here is my angular function:
signUp() {
this.userNotExist = "";
this.userExist="";
this.http.post('/signup',this.signform.value).map((res: any) => res.json())
.subscribe((res: any) => {
console.log('TTTTTTTTT')
console.log(res)
console.log('TTTTTTTTT')
if(res=='EXIST'){
this.userNotExist = "";
this.userExist = 'The email already exists';
}else {
this.userExist = "";
this.userNotExist = 'Congrats! You are now signed up';
window.location.reload();
}
}
),(error: any) => {
console.log(error);
}
}
My Node.js app:
passport.use('local-signup', new LocalStrategy({
// by default, local strategy uses username and password, we will override with email
usernameField : 'email',
passwordField : 'password',
nameMainField : 'nameMain',
firstNameField: 'firstName',
passReqToCallback : true // allows us to pass back the entire request to the callback
},
function(req, email, password, done) {
// find a user whose email is the same as the forms email
// we are checking to see if the user trying to login already exists
User.findOne({ 'local.email' : email }).lean().exec( function(err, user) {
// if there are any errors, return the error
if (err)
return done(err);
// check to see if theres already a user with that email
if (user) {
return done(null, false, req.flash('signupMessage', 'Email already exists.'));
} else {
var newUserS = new User();
// set the user's local credentials
newUserS.local.email = email;
newUserS.local.password = newUserS.generateHash(password); // use the generateHash function in our user model
newUserS.local.nameMain = req.body.firstName + ' ' + req.body.nameMain;
newUserS.local.firstName = req.body.firstName;
newUserS.role=0;
newUserS.profileImage='/assets/fonts/male.png';
// save the user
newUserS.save(function(err, u) {
if (err)
throw err;
return done(null, newUserS);
});
}
});
}));

Answer 1

You are getting xml response instead of JSON response. I am pretty sure it is something like this:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE paymentService PUBLIC "-//WorldPay//DTD WorldPay PaymentService v1//EN"
"http://dtd.WorldPay.com/paymentService_v1.dtd">
<paymentService version="1.4" merchantCode="ExampleCode1"> <!--The merchantCode you supplied originally-->
<reply>
<orderStatus orderCode="ExampleOrder1"> <!--Not present for parse or security violation errors-->
<error code="2">
<![CDATA[Invalid address: Postal code is missing or empty.]]>
</error>
</orderStatus>
</reply>
</paymentService>
The exception comes from the first char at the xml response.