Web Applications
Building a Chat Web Application
It's now time to move onto building a proper web application. Rather than the simple todo application you would build in other systems, for node the standard is a chat application (which is a lot more exciting!).
Primus is a wrapper library over many different WebSockets libraries. WebSockets is a technology that allows browser clients to communicate with servers. Until WebSockets became a thing in 2011, such functionality was achieved via several dodgy workarounds.
We can install Primus for our project like so:
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npm init # setup our project
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npm install --save express # install express, which we will attach Primus to
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npm install --save primus # install Primus
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npm install --save ws # the WebSockets library we will sue with Primus
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Server to Browser Relay
The most basic example of this is the following, which will allow the server to broadcast to all clients, while receiving responses from clients:
socket-server.js
socket-client.html
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'use strict'
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// Requires
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const express = require('express')
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const Primus = require('primus')
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const pathUtil = require('path')
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// Application
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const app = require('express')()
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const server = require('http').createServer(app)
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const primus = new Primus(server, { transformer: 'websockets' })
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// Middlewares
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app.get('/', function (req, res) {
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require('fs').createReadStream(pathUtil.join(__dirname, 'socket-client.html')).pipe(res)
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})
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app.use(function (req, res) {
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res.status(404).send('404 Not Found. 🙁 \n')
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})
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// Socket
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primus.on('connection', function (spark) {
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console.log('connection has the following headers', spark.headers)
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console.log('connection was made from', spark.address)
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console.log('connection id', spark.id)
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// Receive messages
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spark.on('data', function (message) {
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console.log('connection', spark.id, 'sends', message.toString())
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})
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// Send messages
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process.stdin.on('data', function (message) {
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spark.write('The server has spoken: ' + message.toString())
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})
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// Send an initial hello
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spark.write('Hello user. I am the server communicating to you.')
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})
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// Listen
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server.listen(8080)
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<!DOCTYPE html>
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<html>
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<head>
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<title>My Web App</title>
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</head>
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<body>
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<!-- Scripts -->
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<script src="/primus/primus.js"></script>
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<script>
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// Tell primus to create a new connect to the current domain/port/protocol
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var primus = new Primus()
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// Ask for a response if we receive data
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primus.on('data', function (message) {
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alert(message)
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var response = prompt('What would you like to say?')
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if (response) {
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primus.write(response)
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alert('Sent')
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}
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})
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</script>
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Hello.
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</body>
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</html>
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Browser to Browser Broadcasting
A more useful example of this, is your basic chat app, which allows clients to broadcast to other clients:
chat-server.js
chat-client.html
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'use strict'
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// Requires
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const express = require('express')
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const Primus = require('primus')
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const pathUtil = require('path')
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// Application
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const app = require('express')()
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const server = require('http').createServer(app)
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const primus = new Primus(server, { transformer: 'websockets' })
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// Middlewares
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app.get('/', function (req, res) {
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require('fs').createReadStream(pathUtil.join(__dirname, 'chat-client.html')).pipe(res)
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})
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app.use(function (req, res) {
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res.status(404).send('404 Not Found. 🙁 \n')
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})
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// Socket
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primus.on('connection', function (spark) {
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console.log('connection has the following headers', spark.headers)
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console.log('connection was made from', spark.address)
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console.log('connection id', spark.id)
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// Receive messages
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spark.on('data', function (message) {
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// Broadcast them back to everyone
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primus.write('user ' + spark.id + ' sends ' + message.toString())
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})
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// Send an initial hello
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spark.write('Hello user ' + spark.id + '. I am the server communicating to you.')
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})
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// Listen
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server.listen(8080)
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<!DOCTYPE html>
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<html>
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<head>
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<title>My Web App</title>
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<style>
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.messages {
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max-height: 500px;
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border: 1px solid gray;
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overflow: auto;
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}
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.messageInput {
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width: 100%;
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padding: 1em;
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}
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</style>
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</head>
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<body>
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<!-- App -->
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<div class="app">
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<ul class="messages"></ul>
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<input type="text" disabled class="messageInput" placeholder="Enter your message here" />
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</div>
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<!-- Scripts -->
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<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0-beta1/jquery.min.js"></script>
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<script src="/primus/primus.js"></script>
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<script>
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// Tell primus to create a new connect to the current domain/port/protocol
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var primus = new Primus()
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// Ready
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$(function () {
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// Fetch
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var $app = $('.app')
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var $messages = $app.find('.messages')
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var $messageInput = $app.find('.messageInput')
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// Enable input once connection is open
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primus.on('open', function () {
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$messageInput.removeAttr('disabled').focus()
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})
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// Receive message
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primus.on('data', function (message) {
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$message = $('<li>', {
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'class': 'message',
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text: message
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})
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$messages.append($message)
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})
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// Send message
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$messageInput.on('keypress', function (event) {
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if (event.keyCode === 13) { // enter
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var message = $messageInput.val().trim()
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primus.write(message)
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$messageInput.val('') // clear input
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}
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})
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})
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</script>
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</body>
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</html>
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Where can this go?
It is now your turn to have a go and mash up your own solution. To help you get started, here are a bunch of ideas on how you can extend the chat application:
- Chat Rooms
- Add support for two chat rooms
- Add support for unlimited chat rooms
- Allow users to change the names of the chat rooms
- Users
- Give each user a randomly generated name - e.g.
User ${Math.random()} - Next to each message, show the user who sent it - e.g.
${user.name} says: ${message.text} - Show user connection and disconnection events as messages in the chat - e.g.
${user.name} joined the chat" - Remember the user's details if they leave the page and come back - e.g. localstorage or sessions
- Allow the user to change their name
- Show user name change events as messages in the chat - e.g.
${oldName} changed their name to ${newName} - Give each user their own randomly selected color - e.g.
style="color: hsl(50,50,50);" - Create a sidebar that lists all active members in the chat room
- Allow users to specify their email
- If a user has an email specified, display their avatar next to their username in the message listing
- When a user changes their details, automatically update all prior mentions of their details
- Abstractions
- Messages
- Relative times
- Markdown support
- Webkit notifications
Last modified 3yr ago