Send variables to layout - node.js

Question

I'm learning how to build web applications using Node.js and express, so I'm really noob yet.
So, I have some questions here. I'm building a landing page, and all the informations that I'm getting from my Database (in mysql) will appear in a single page.
I'm sending values from my database, to my layout, built in Jade.
And I created multiple functions to get specific data, here an example:
function getUser(username, userId, callback) {
connection.query('SELECT * FROM users WHERE user_id = ?', userId, function(err, result) {
if (err)
callback(err, null);
else
var callBackString = {};
callBackString.value1 = result[0].user_email;
callBackString.value2 = result[0].user_name;
callback(null, callBackString);
});
}
When the user tries to login I check if the user exists to change the layout and send to the layout some important values:
router.post('/login', function(req, res) {
connection.query('SELECT user_id FROM users WHERE user_email = ? AND user_password = ?', [req.body.login, req.body.password], function(err, results) {
if (err) throw err;
if (results[0]) {
userId = results[0].user_id;
getUser("username", userId, function(err, data) {
if (err) {
console.log("ERROR : ", err);
} else {
res.render('logged_in', {
email: data.value1,
username: data.value2,
});
res.end();
}
});
} else {
res.render('index', {
validation: "failed"
});
}
});
});
I'm only calling one function here (getUser()), and when I call this function, the layout changes, and I send some values.
But now I would like to create a new function called getPosts(), to get informations from a different table, and send it to the layout too, like I did when i called the function getUser()
I tried to do something like this but I had no success, when I call the variables outside the scope I keep getting "undefined".
router.post('/login', function(req, res) {
connection.query('SELECT user_id FROM users WHERE user_email = ? AND user_password = ?', [req.body.login, req.body.password], function(err, results) {
if (err) throw err;
if (results[0]) {
userId = results[0].user_id;
getUser("username", userId, function(err, data) {
if (err) {
console.log("ERROR : ", err);
} else {
email = data.value1;
username = data.value2;
}
});
getPosts("posts", 1, function(err, data) {
if (err) {
console.log("ERROR : ", err);
} else {
postName = data.value1;
postText = data.value2;
}
});
res.render('logged_in', {
email: email,
username: username,
pstname: postName,
psttxt: postText
});
res.end();
} else {
res.render('index', {
validation: "failed"
});
}
});
});
What do I need to change on my code? Thank you.

Answer 1

You should read about asynchronization in node.js so if you change your code as bellow it may work:
router.post('/login', function(req, res) {
connection.query('SELECT user_id FROM users WHERE user_email = ? AND user_password = ?', [req.body.login, req.body.password], function(err, results) {
if (err) throw err;
if (results[0]) {
userId = results[0].user_id;
getUser("username", userId, function(err, data) {
if (err) {
console.log("ERROR : ", err);
} else {
email = data.value1;
username = data.value2;
getPosts("posts", 1, function(err, data) {
if (err) {
console.log("ERROR : ", err);
} else {
postName = data.value1;
postText = data.value2;
res.render('logged_in', {
email: email,
username: username,
pstname: postName,
psttxt: postText
}
});
}
});
} else {
res.render('index', {
validation: "failed"
});
}
});
});