How to fix the node.js code to check for login - mysql

Question

I am new to node js and dont know why is this returning the false value always. I have form made in html that sends post request then the app.js calls login.js function and checks the database
I tried to manually input with 2 var and it works but when using the form it doesnt.
app.post('/login', urlencodedParser, function (req, res) {
var check = require('./js/login.js');
var username = req.body.username;
var password = req.body.password;
if(check([username,password]) == true){
console.log('fine');
res.render('index');
}
else{
console.log('get lost');
res.render('login');
}
});
This is the app.js code thet calls the login.js but the page doesnt render also even if the returned value is incorrect.
var check = function(arr){
var con = require(__dirname + '/database.js');
var login_check = false;
con.connect(function(err) {
if (err) throw err;
con.query("SELECT * FROM users WHERE (name = ?) AND (password = ?)", [arr[0], arr[1]], function (err, result, fields) {
if (err) throw err;
if(result)
{
login_check = true;
}
});
});
return login_check;
};
module.exports = check;

Answer 1

Because of your con.query function is asynchronous, so the return of function will always be false by default (it returns before executing check). Another way, you can try to use callback function as my suggestion code below:
app.post("/login", urlencodedParser, function(req, res) {
var check = require("./js/login.js");
var username = req.body.username;
var password = req.body.password;
var checkCallback = function (isLogin) {
if (isLogin) {
console.log("fine");
res.render("index");
} else {
console.log("get lost");
res.render("login");
}
}
check([username, password], checkCallback);
});
// -----------------------------
// login.js
var check = function(arr, callback) {
var con = require(__dirname + "/database.js");
var login_check = false;
con.connect(function(err) {
if (err) throw err;
con.query(
"SELECT * FROM users WHERE (name = ?) AND (password = ?)",
[arr[0], arr[1]],
function(err, result, fields) {
if (err) throw err;
if (result) {
login_check = true;
callback(true); // Call the callback function here after checking is done
}
}
);
});
return login_check;
};
module.exports = check;