Develop Reference

extract value after the endpoint and assign it to a child function in Java Script using Express

I am just 2 days old in JS, so, asking a question that may sound a basic one.
I have a server running at localhost:8000/api/namespace.
const express = require('express');
const app = express();
app.get('/', function (req, res) {
res.send('Welcome to deletion task!!!');
});
app.get('/api/namespace/:namespaceName', function (req, res) {
namespaceName = res.send(req.params);
console.log(`${namespaceName}`);
});
var server = app.listen(8000, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Example app listening at http://%s:%s', host, port);
});
The output of console.log(`${namespaceName}`); is object obect
On accessing URL as http://localhost:8000/api/namespace/abcd, it is giving the output as {"namespaceName":"abcd"}.
What I am trying to achieve is to get the value "abcd" into a variable and pass it into a child process as an argument(${namespaceName}) to a shell script.
var child_process = require('child_process');
child_process.execFile('./restart.sh', [`${namespaceName}`],
function (error, stdout, stderr) {
if (error !== null) {
console.log(error);
} else {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
}
});
I am not able to achieve it.
Help, please.

Triggering socket.io real-time notifications from Express 4 middleware

I am building a real-time notification system using socket.io. This is my server-side code at the moment:
bin/www:
var app = require('../app');
var server = http.createServer(app);
var io = app.io
io.attach(server);
server.listen(port, function(err) {
if (err) console.log(err);
console.log('Listening on port ' + port + '...');
});
app.js:
var socket_io = require('socket.io');
var express = require('express');
var app = express();
var io = socket_io();
app.io = io;
require('./config/socket')(app.io);
config/socket.js:
var User = require('../controllers/user');
module.exports = function (io) {
io.on('connection', function (socket) {
console.log('Socket.io connected');
socket.emit('connection', "Connection created.");
socket.on('send notification', function(data) {
User.createNotification(socket.request.user, data);
});
});
};
routes/index.js:
var express = require('express');
var User = require('../controllers/user');
var router = express.Router();
router.post('/order', User.order);
module.exports = router;
controllers/user.js:
var User = require('../models/user').model;
var io = require('socket.io');
module.exports = {
order: function(req, res) {
/* some create order code */
io.emit('send notification', 'Your order was successful!');
res.sendStatus(200);
}
}
I keep getting the error TypeError: io.emit is not a function whenever I try to call the route POST /send even though I am clearly initiating socket.io in my app.js and bin/www files and requiring it in controllers/user.js. All the examples I've seen online emit notifications from within this part:
io.on('connection', function (socket) {
socket.emit(event, msg);
});
but I want my notifications to be triggered from the middleware so I can send custom notifications to the user when certain events happen in the application backend.

Try the following instead:
io.on('connection', function(socket){
socket.on('xxx', function(obj){
io.emit('xxx', {xxx: xxx})
})
})
This should suppress your TypeError:.

Socket.io socket emit not being called

I have this index.js file on the client:
var socket;
var init = function() {
// Setup Socket:
socket = io.connect();
// Setup Event Handlers:
setEventHandlers();
// Connect to Server:
socket.emit('connect', {
name : "User Name"
});
console.log("Client Init Complete.");
}
var setEventHandlers = function() {
// Set Routes For Connections
socket.on("connection resp", onConnected);
}
var onConnected = function(data) {
console.log(data.resp);
}
And I have this code on the server:
// SETUP:
var express = require('express');
var app = express();
var http = require('http').Server(app);
var request = require('request');
var path = require('path');
var socket = require('socket.io')(http);
var server_port = process.env.OPENSHIFT_NODEJS_PORT || 8080;
var server_ip_address = process.env.OPENSHIFT_NODEJS_IP || '0.0.0.0';
var bodyParser = require('body-parser')
var fs = require('fs');
// SETUP:
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
extended : false
}));
app.configure(function() {
app.use(express.static(path.join(__dirname, 'public')));
})
var setEventHandlers = function() {
socket.sockets.on("connection", onInit);
};
var onInit = function(client) {
client.on("connect", onConnect);
};
var onConnect = function(data) {
console.log("Called");
}
// Send index page html
app.get('/', function(req, res) {
res.sendfile("public/html/index.html");
});
// Turn on server
http.listen(server_port, server_ip_address, function() {
console.log("App Listening on " + server_ip_address + ", server_port "
+ server_port);
});
setEventHandlers();
The issue is that on the onConnect on the server is never called. Eventhough I call socket.emit("connect") on the client.
After further testing, it seems that the socket id is undefined: this.id returns undefined.

You need to add quotes to the parameters in the socket.emit function like this:
// Connect to Server:
socket.emit('connect', {
'name' : 'User Name'
});

You should initialize your socket variable through io.connect("server address") and has i see in your code you have not passed any parameter to io.connect
.If server is in your local machine then connect to it by io.connect("http://localhost").
For more information see Docs. socket.io-client

Show database content in browser with node.js, MySQL and Jade

I'm currently working with Node.js, Express.js and Jade. My database is MySQL. I'm new to node.js, so I thought I try something very easy: Displaying some data from the database in a table in the browser.
Unfortunately it still doesn't work. I can display data on an free port but not where I need it - on port 3000. And I also can't work with the response itself. This is one of the "solutions" or ideas I had. Maybe there is a problem with the asynchronous call? I simply have no idea.
Here is my code:
routes.js
var express = require('express');
var controller = express.Router();
var dataModel2 = require('../models/rooms');
controller.get('/rooms', function(req, res, next) {
var rooms = dataModel2();
res.render('rooms', {
items: rooms
});
});
module.exports = controller;
models/rooms.js
var rooms;
var connection = require('./databaseConnection');
var http = require('http');
rooms = function() {
http.createServer(function (request, response)
{
console.log('Creating the http server');
connection.query('SELECT * FROM rooms', function(err, rows, fields)
{
response.writeHead(200, { 'Content-Type': 'application/json'});
var room = response.end(JSON.stringify(rows));
return room;
});
});
module.exports = rooms();
models/databaseConnection.js
var mysql = require('mysql');
module.exports = mysql.createConnection({
host : 'localhost',
user : 'root',
password : '',
database : 'raspi_key_royal'
});
rooms.jade
extends layout
block content
div(id="bodyRoyal")
table(border='1')
thead
tr
th ID
th Name
tbody
each item in items
tr
td=item.rid
td=item.name
I splitted the functions a bit because there are some other sections like "persons" etc. I tried to insert console.logs in the rooms.js but that doesn't seem to work.
I also thought I could save the response into a variable so that I can work with it somewhere else.
Thank you for every help and hints!
Steffi

Something like this should do it:
var express = require('express'),
app = express(),
connection = require('./databaseConnection');
app.get('/rooms', function (req, res) {
connection.query('SELECT * FROM rooms', function(err, rows, fields)
{
res.render('rooms', {
items: rows
});
});
});
var server = app.listen(3000, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Example app listening at http://%s:%s', host, port);
});

This is from the express site...http://expressjs.com/starter/hello-world.html
app.listen(3000, ...
is the how to configure a it to a specific port (in this case 3000).
var express = require('express');
var app = express();
app.get('/', function (req, res) {
res.send('Hello World!');
});
var server = app.listen(3000, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Example app listening at http://%s:%s', host, port);
});

Setting up a MongoDB database connection with node.js

How would I set up a MongoDB database connection with node.js?
Here is my app.js file:
var express = require('express'),
app = express(),
server = require('http').createServer(app),
io = require('socket.io').listen(server);
server.listen(3000);
app.get('/', function(req, res) {
res.sendfile(__dirname + '/index.htm');
});
app.use(express.static(__dirname + '/assets'));
io.sockets.on('connection', function(socket) {
socket.on('send message', function(data) {
io.sockets.emit('new message', data);
});
});
I have already set-up MongoDB and have it running as a service on Windows.

As of 1.2, the recommended way to perform a connection is in documentation:
http://mongodb.github.io/node-mongodb-native/driver-articles/mongoclient.html
excerpt:
var MongoClient = require('mongodb').MongoClient
, Server = require('mongodb').Server;
var mongoClient = new MongoClient(new Server('localhost', 27017));
mongoClient.open(function(err, mongoClient) {
var db1 = mongoClient.db("mydb");
mongoClient.close();
});
You may find that a connection singleton is useful for the current state of the official node.js driver. Below is some sample code that I use:
connection.js module:
var MongoClient = require('mongodb').MongoClient;
var db_singleton = null;
var getConnection= function getConnection(callback)
{
if (db_singleton)
{
callback(null,db_singleton);
}
else
{
//placeholder: modify this-should come from a configuration source
var connURL = "mongodb://localhost:27017/test";
MongoClient.connect(connURL,function(err,db){
if(err)
log("Error creating new connection "+err);
else
{
db_singleton=db;
log("created new connection");
}
callback(err,db_singleton);
return;
});
}
}
module.exports = getConnection;
Referencing module:
var getConnection = require('yourpath/connection.js')
function yourfunction()
{
getConnection(function(err,db)
{
//your callback code
}
.
.
.
}