NodeJs check username and password return null

Question

I'm trying to check the entered username and password stored in a database. My solution is not correct and I think there might be something better than my code.

Here it is thus far:

function login (username, password, callback) {
    var query = "SELECT  * FROM users WHERE username = ?";

    connection.query(query, [username], function (err, results) {
        if (err) return callback(err);
        if (results.length === 0) return callback();
        var user = results[0];

        if (!bcrypt.compareSync(password, user.password)) {
            return callback();
        }

        callback(null,   {
            id:          user.id.toString(),
        });

    });
}
app.get('/salam', function (req, res) {
    var username = 'mahdi';
    var originalPassword = 'a';

    login(username , originalPassword,function (callback) {
        console.log(callback);
    });
});

In my code, console.log(callback); returns null, but usernames and passwords are correct. How can I fix this?

You are already setting first parameter of callback as a NULL? callback(**null**, { id: user.id.toString(), }); — Tuğca Eker
– Tuğca Eker, Commented Aug 1, 2016 at 12:15

Rayon · Accepted Answer · 2016-08-01 12:19:51Z

In your success callback function, you are having 2 arguments but in error callback, only one argument.

In error and success case, value of first parameter will always be null and in if (!bcrypt.compareSync(password, user.password)) { case, value of first argument will be undefined as there is no value being passed as argument.

Suggestion: Use first argument as Boolean(false or true) and based on the value, handle the callback.

function login(username, password, callback) {
  var query = "SELECT  * FROM users WHERE username = ?";

  connection.query(query, [username], function(err, results) {
    if (err) return callback(false);
    if (results.length === 0) return callback();
    var user = results[0];

    if (!bcrypt.compareSync(password, user.password)) {
      return callback(false);
    }
    callback(true, {
      id: user.id.toString(),
    });

  });
}
app.get('/salam', function(req, res) {
  var username = 'mahdi';
  var originalPassword = 'a';

  login(username, originalPassword, function(success, value) {
    if (success) {
      console.log(value);
    }
  });
});

It won't always be null: there are two places in the OP's code (and one place in yours) where the function is called with no arguments, so then callback will be undefined.
@Rayon Thanks, problem resolved sir :) wait to me for accept that
@Rayon hi, could you help me on this topic? stackoverflow.com/q/38794164/6599627 Thanks

Ebrahim Pasbani · Accepted Answer · 2016-08-01 12:26:40Z

It should be, because you didn't pass anything in callback. Change like this :

function login (username, password, callback) {
    var query = "SELECT  * FROM users WHERE username = ?";

    connection.query(query, [username], function (err, results) {
        if (err) return callback(err);
        if (results.length === 0) return callback(null, false);
        var user = results[0];

        if (!bcrypt.compareSync(password, user.password)) {
            return callback(null, false);
        }

        callback(null,   true, {
            id:          user.id.toString(),
        });

    });
}
app.get('/check', function (req, res) {
    var username = 'mahdi';
    var originalPassword = 'a';

    login(username , originalPassword,function (err, result, id) {
        console.log(err);
        console.log(result);
        console.log(id);
    });
});

result is for finding out true|false of action. And id means when result is true

Also err for callback is needed to error handling

If you don't pass anything (which is the case in two places) the argument will be undefined, not null. But in what I assume it's the success case the OP's code explicitly passes null.

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