Route example

nodejsExample.js

router.post('/userInfo', function(req, res){ // Route for handling the request
    jwt.verify(req.body.token, JWT_SECRET, (err, decoded) => { // Checking if the JWT token of the user is valid
        if (err){ // Handling error
            res.json({
                "info" : "Error0"
            });
        }else{
            if(typeof decoded.username === "undefined"){ // Checking if username is defined in the request
                res.json({ // Handling the error
                    "info" : "Error1"
                });
            }else{
                var query = "SELECT u.NAME AS name, u.last_name, u.about, s.NAME AS school, u.profile_pic,  u.goldMedals, u.silverMedals, u.bronzeMedals FROM Users u\
                LEFT JOIN Schools s ON u.School = s.school_id WHERE u.username = ?"; // MYSQL query 
                connection.query(query,[decoded.username], function(error, rows, fields){ // Querying 
                    if(error){ // Handling any error occured during querying
                        console.log("There was an error: " + error.stack); 
                        res.json({res:false});
                        return;
                    }
                    var info = rows[0]; // Returning the query.
                    res.json(info);
                });
            }
        }
      });
});