Express routing with a login action using SQLite

Question

I'm new to Express and SQL, so I don't know the conventional ways of combining the two. Right now I have done it the following way:

app.get('/login', function (req, res) {
 res.render('login');
});
app.get('/home', function (req, res) {
 res.render('home');
});
app.post('/login', function (req, res) {
 db = new sqlite3.Database(file);
 db.serialize(function () {
 [...]
 db.all(query, function (err, rows) {
 if(rows.length == 1) {
 [...]
 res.render('home', {
 username: rows[0].username
 });
 }
 else {
 res.render('login', {
 message: "Login not successful!"
 });
 }
 });
 });
 db.close();
});

However, I feel like the routing should be separated from the database stuff. What should I do different? Or is this normal?

Answer 1

For larger projects this can get very complicated and nasty. You can refactor the db access into functions that take a callback as a parameter. Example:

// db_helper.js
module.exports.isUserAuthenticated = function(query, callback) {
 [db code here]
 callback(err, rows);
};

And then in your routes file:

// app.js
var db_helper = require('./path/to/db_helper.js');
....
app.post('/login', function(req, res) {
 var query = [parse from request object]
 db_helper.isUserAuthenticated(query, function(err, rows) {
 if (rows.length == 1) {
 [...]
 res.render(...);
 } else {
 [...]
 res.render(...);
 }
 });
});

Node-style callbacks typically have an error as the first parameter (null if there was no error), and associated data in other parameters.

Nesting callbacks can be a pain if this gets more complicated, so I suggest you look into Promises or async

• omgimanerd: You're welcome. I highly suggest looking into async since it can streamline your db_helper.js a lot.