'Cannot read property 'length' of undefined' nodeJS - node.js

Question

I'm getting started in Node.js and I'm completely confused as to why I can't get the results of my SQL query to render on a page, i'm using sqlite3.
This is a part of my index.js file
router.get('/students', function (req, res, module) {
var fs = require("fs");
var file = "./test.db";
var exists = fs.existsSync(file);
if (!exists) {
console.log("Creating DB file.");
fs.openSync(file, "w");
}
var sqlite3 = require("sqlite3").verbose();
var db = new sqlite3.Database(file);
db.serialize(function () {
if (!exists) {
db.run("Create table students ( ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL UNIQUE, Nom varchar (255), Prenom varchar (255) );");
}
});
db.all('SELECT * FROM students', function selectCb(err, rows, fields) {
if (err) {
throw err;
}
for (var i in rows) {
console.log(rows[i]);
}
res.render('showResults.jade', {
results: rows
});
});
db.close();
res.render('students', { title: 'list' });
});
This is my Jade (create.jade) file;
block content
form(method='get', action='/students/create')
button(type='submit') Creer
ul
each item, i in results
li #{item.Nom} (#{item.Prenom})
li= JSON.stringify(item)
I put all of this things in my express app, I launch it with my shell, I receive all the sql data like this:
{ ID: 1, Nom: 'zeze', Prenom: 'zeze' }
{ ID: 2, Nom: 'ertty', Prenom: 'uuuuuuuuuuu' }
But my /students page show a message
http://i.stack.imgur.com/ormUG.png
Could you please help me, I'm really desperate.
(Sorry for my bad english I'm French) ^^

Answer 1

res.render('students', { title: 'list' });
and this line
each item, i in results
The variable names do not match.
From the picture, I can see that you are rendering the page called students.jade. For that page, you are sending variable title to Jade but you declared that the variable would be called results in Jade.

Answer 2

Have you tried removing the second res.render call?
It is possible that it is the one being called instead of the first one since the async call to the DB is not yet finished when the execution reaches the second res.render call.

Answer 3

db.close() should be moved inside the query's callback because it closes the db connection before the query has the chance to finish. Here is the revised code:
db.all('SELECT * FROM students', function selectCb(err, rows, fields) {
if (err) {
db.close(); // <<<<<<<<<<<<<<
throw err;
}
for (var i in rows) {
console.log(rows[i]);
}
res.render('showResults.jade', {
results: rows
});
db.close(); // <<<<<<<<<<
});