Node.js/Express Async functions

Question

I'm playing with node.js and express. I have a little server which fetch sqlite contents and send everything to a Jade template. It works fine using this code :

var express = require('express');
var app = express();
app.set('view engine', 'jade');
var async = require('async');

var result_title = [];
var result_scope = [];
var result_benefits = [];
var result_technical = [];

app.use(express.static(__dirname + '/views'));

app.get('/product1', function(req, res){

  var sqlite3 = require('sqlite3').verbose();
    var db = new sqlite3.Database('products.db');
    var check;
    db.serialize(function() {
        db.each("SELECT title, scope, body, technical_information FROM products", function(err, row) {
          result_title.push(row.title);

            result_scope.push(row.scope);

            result_benefits.push(row.body);

          result_technical.push(row.technical_information);
        });

    });

  console.log(result_title[0]);

    res.render("index", {title:result_title[0], scope:result_scope[0],benefits:result_benefits[0], technical_information:result_technical[0]});


    db.close();

});

app.listen(8080);

My issue is that when I go to page http://localhost/product1:8080 nothing is displayed. A manual refresh of the page is needed to load the content! My research tells me that I need to use Async functions. I edited my code :

var express = require('express');
var app = express();
app.set('view engine', 'jade');
var async = require('async');

var result_title = [];
var result_scope = [];
var result_benefits = [];
var result_technical = [];

app.use(express.static(__dirname + '/views'));

app.get('/product1', function(req, res){

  var sqlite3 = require('sqlite3').verbose();
    var db = new sqlite3.Database('products.db');
    var check;

  async.series([
    function(callback) {
         db.serialize(function() {
             db.each("SELECT title, scope, body, technical_information FROM products", function(err, row) {
               result_title.push(row.title);

                 result_scope.push(row.scope);

                 result_benefits.push(row.body);

               result_technical.push(row.technical_information);
             });

         });
     },
     function(callback) {
       // console.log(result_title[0]);
          res.render("index", {title:result_title[0], scope:result_scope[0],benefits:result_benefits[0], technical_information:result_technical[0]});

        db.close();
      }
    ], function(error, results) {
      console.log('');
    })
});

app.listen(8030);

But the webpage is loading, loading and nothing happens.. I made something wrong, but no idea where for the moment. If someone have an idea it could be great ;-) Thanks!

Answer 1

Your url is wrong also the second code block your port is different.

Give port name after domain or ip address , if not the request will go /product1:8080 and you haven't any router like that , so request goes to error page also it semes you haven't any error handling for 404.

Try : http://localhost:8080/product1 or http://localhost:8030/product1

Also you have an issue in your second code block :

res.render("index", {title:result_title[0], scope:result_scope[0],benefits:result_benefits[0], technical_information:result_technical[0]});

This line should be executed in all series callback, If not you will not get data you want. Because it's still in async function.

], function(error, results) {
   res.render("index", {title:result_title[0], scope:result_scope[0],benefits:result_benefits[0], technical_information:result_technical[0]});
})

---

I have just investigated sqllite3 , you don't need to use async library as an extra in this situation(BTW in async functins you have to call callback with return parameter on it). In sqllite3 documentation db.each .

That latest code should work. Try following.

var express = require('express');
var app = express();
app.set('view engine', 'jade');
var async = require('async');

var result_title = [];
var result_scope = [];
var result_benefits = [];
var result_technical = [];

app.use(express.static(__dirname + '/views'));

app.get('/product1', function(req, res){

  var sqlite3 = require('sqlite3').verbose();
    var db = new sqlite3.Database('products.db');
    var check;

  db.serialize(function() {
     db.each("SELECT title, scope, body, technical_information FROM products", function(err, row) {
       result_title.push(row.title);

         result_scope.push(row.scope);

         result_benefits.push(row.body);

       result_technical.push(row.technical_information);
     },function(err, rows){
        if(err){
            // handle error
        }
        res.render("index", {title:result_title[0], scope:result_scope[0],benefits:result_benefits[0], technical_information:result_technical[0]});
     });
    });
});

app.listen(8080);