Insert data into res.body back to client - json

Question

with my client js i have perform a fetch and send along some data.
And i've attempted to do a res.send or res.json to send a result back.
Do I need to create a new json and send it?
Express Server
const express = require('express');
const app = express();
const pg = require('pg');
const conString = 'postgres://postgres:password#localhost/postgres';
const bodyParser = require('body-parser');
app.use(bodyParser.json()); //support json encoded bodies
app.use(bodyParser.urlencoded({ extended: true})); //support encoded bodies
app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
next();
});
app.listen(3000, function () {
console.log('Server listening on port 3000!');
});
app.post('/', function(req, res){
var uname = req.body.username;
var pw = req.body.password;
QueryByUserName(uname, function(err, result){
if(err){
console.error('error happened', err);
//handle error
}
if(uname == result.username){
//name is in our database
if(pw == result.password){
console.log("User and Password Correct!");
res.json({ message: 'correct' });
} else {
console.log("Password Incorrect!");
res.json({ message: "incorrect" });
}
} else if(result.username == "undefined"){ //placeholder
console.log("username does not exist");
res.send( {message: "dne"} );
console.log(res);
}
});
});
function QueryByUserName(input, callback) {
pg.connect(conString, function(err, client, done){
if(err){
callback(err);
return;
}
client.query(SelectAll(), function(err, result){
//Query database for all usernames
done();
var isFound = false;
for(var x = 0; x < result.rows.length; x++){
//loop through all usernames from database.
if(result.rows[x].username == input){
isFound = true;
//username exists, now we obtain the rest of the data.
client.query(findDataInDatabase(input, '*'), function(err, result){
done();
if(err){
callback(err);
return;
}
console.log(result.rows[0]);
callback(null, result.rows[0]);
//return all information regarding user to callback function
});
} else if(x == (result.rows.length - 1) && !isFound){
callback(null, {username: "undefined"}); //placeholder
//Username does not exist in database
}
} //end of For Loop
});
});
}
function findDataInDatabase(username, WhatWeLookingFor) {
return 'select ' + WhatWeLookingFor + ' from users where username = \'' + username + '\'';
}
Express server side will try to send a message to the client.
but when I do this i did a console.log(res) it shows that the body is { null, null, null}
Client login Function
handleLogin: function(){
let fetchData = {
method: "post",
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify({
username: this.state.user,
password: this.state.password,
message: null
})
}
var fromServer = fetch('http://localhost:3000/', fetchData)
.then(function(response){
if( !response.ok){
throw Error (response.statusText);
}
console.log(response);
console.log(response.message);
console.log(response.body);
console.log(response.body.text);
return response.json();
})
.catch(error => console.log("there was an error --> " + error));
},
Edit : Screenshots below

Answer 1

Since you have returned, res.json({ message: 'correct' });
use,
response.message
Instead of,
response.body
var fromServer = fetch('http://localhost:3000/', fetchData)
.then(response => response.json())
.then(response => {
console.log(response.message);
})

Answer 2

After talking to Sraven, who was a huge help.
The code is sending a req, and the server is responding with a response with the message included. The problem was on the client side where it was not getting the response correctly.
Below is the working code and was able to finally produce a response.
var fromServer = fetch('http://localhost:3000/', fetchData)
.then(response => response.json())
.then(response => {
console.log(response.message);
})