Rachel Cole

Rachel Cole

1564563883

How to build a real time chat application in Node.js using Express, Mongoose and Socket.io

In this tutorial, we will use the Node.js platform to build a real time chat application that sends and shows messages to a recipient instantly without any page refresh. We will use the JavaScript framework Express.js and the libraries Mongoose and Socket.io to achieve this.

Before we start, lets have a quick look at the basics of Node.js

Node.js

Node.js is an open-source, cross-platform JavaScript run-time environment that executes JavaScript code outside the browser. The most important advantage of using Node is that we can use JavaScript as both a front-end and back-end language.

As we know, JavaScript was used primarily for client-side scripting, in which scripts were embedded in a webpage’s HTML and run client-side by a JavaScript engine in the user’s web browser.

Node.js lets developers use JavaScript to write Command Line tools and for server-side scripting — running scripts server-side to produce dynamic web page content before the page is sent to the user’s web browser.

To install node:

https://nodejs.org/en/download/

Even though the node is single threaded it’s still faster to use asynchronous functions. For example, Node can process other things while a file is being read off disk, or while waiting for an HTTP request to complete. The asynchronous behaviour can be implemented using callbacks. Also the JavaScript works well with JSON and No-SQL databases.

NPM** Modules**

Nodejs allows the modules of libraries to be included in the application. These modules can be user-defined or third party modules.

The third party modules can be installed using the following command:

npm install module_name

and the installed modules can be used using the require() function:

var module = require(‘module_name’)

In Node apps we will be using a package.json file to maintain the module versions. This file can be created by this command:

npm init

and the packages must be installed as follows:

npm install -s module_name

There are many frameworks that can be added as modules to our Node application. These will be explained further on as needed.

Simple Chat Application

The app must allow multiple users to chat together. The messages must be updated without refreshing the page. For simplicity we will be avoiding the authentication part.

We can start by creating a new project directory and moving into it. Then we can initiate our project by the following command:

npm init

This will prompt us to enter details about our project.

After this a package.json file will be created:

{

 “name”: “test”,

 “version”: “1.0.0”,

 “description”: “”,

 “main”: “index.js”,

 “scripts”: {

 “test”: “echo \”Error: no test specified\” && exit 1"

 },

 “author”: “”,

 “license”: “ISC”

}

Our app directory is now set.

The first thing we need to create is a server. In order to create that, we will be making use of a framework named Express.

Express.js

Express.js, or simply Express, is a web application framework for Node.js. Express provides a robust set of features for web and mobile applications. Express provides a thin layer of fundamental web application features, without obscuring Node.js features.

We will install Express.js using the following command:

npm install -s express

Inside the package.json file a new line will be added:

dependencies”: {

 “express”: “⁴.16.3”

 }

Next we will create a server.js file.

In this file we need to require Express and create a reference to a variable from an instance of Express. Static contents like HTML, CSS or JavaScript can be served using express.js:

var express = require(‘express’); 
var app = express();

and we can start listening to a port using the code:

var server = app.listen(3000, () => {

 console.log(‘server is running on port’, server.address().port);

});

Now we need to create an HTML file index.html that displays our UI. I have added bootstrap and JQuery cdn.

//index.html

 

<!DOCTYPE html>

<html>

<head>

 <! — include bootstap and jquery cdn →

</head>

<body>

<div class=”container”>

 <br>

 <div class=”jumbotron”>

 <h1 class=”display-4">Send Message</h1>

 <br>

 <input id = “name” class=”form-control” placeholder=”Name”>

 <br>

 <textarea id = “message” class=”form-control” placeholder=”Your Message Here”>

</textarea>

 <br>

 <button id=”send” class=”btn btn-success”>Send</button>

 </div>

 <div id=”messages”>

 

</div>

</div>

<script>

 

</script>

</body>

</html>


Please note that the empty

#node-js #express #mongodb

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How to build a real time chat application in Node.js using Express, Mongoose and Socket.io

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1618120954

Real Time Chat App using Node JS Express Socket IO

Real time chat with nodejs socket.io and expressjs. In this tutorial, you will learn how to build real time chat with nodejs socket.io, jquery and expressjs.

This tutorial will help you step by step to on how to build chat application using Nodejs, Express and Socket.IO.

How to build chat application using Nodejs, Express and Socket.IO

Follow the following steps and create chat application using Nodejs, Express and Socket.IO:

  • Step 1 - Create Chat App Directory
  • Step 2 - Install Node Express JS, Socket.io and jQuery
  • Step 3 - Create Index.html and Style.css
  • Step 4 - Create Chat.js
  • Step 5 - Create index.js
  • Step 6 - Run Development Server

https://www.tutsmake.com/node-js-express-socket-io-chat-application-example/

#node js chat application #node js chat application tutorial #real time chat with nodejs socket.io and expressjs #node js chat application with mysql

Jessica Smith

Jessica Smith

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NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

  • Fast startup without relying on a custom version of Node.js.
  • Small artifact (current size is around 1.2MB).
  • First class macros.
  • Support building small TUI apps using Reagent.
  • Complement babashka with libraries from the Node.js ecosystem.

Requirements

Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)
                                        body))))
            body
            binding-pairs)))

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "https://clojure.org")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "https://clojure.org")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.

Dependencies

NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.

Classpath

To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [foo.bar :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"

Reagent

Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink

ink-demo.cljs:

(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))

Promesa

Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))
$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3

Also see API docs.

Js-interop

Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

  • destructuring using :syms
  • property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

API

See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.

Build

Prequisites:

  • babashka >= 0.4.0
  • Clojure CLI >= 1.10.3.933
  • Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

  • Clone and cd into this repo
  • bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb 
License: EPL-1.0

#node #javascript

Nandu Singh

Nandu Singh

1590640889

Build a Real Time Chat App with Socket.io and Node.js

In this video you will be creating a real time chat application complete with usernames and connect/disconnect messages. You will use Socket.io to manage real time web socket connections to a Node.js server that will allow you to communicate real time chat messages to all clients connected to a single server.

This entire project will take less than 100 lines of JavaScript and almost no HTML/CSS, but it is incredibly powerful what can be done with such little code. By the end of this video you will have a strong understanding of how to send and receive messages using web sockets and Socket.io to make any real time application.

📚 Materials/References:

GitHub Code: https://github.com/WebDevSimplified/Realtime-Simple-Chat-App
Socket.io: https://socket.io

#socket-io #node #node.js #chat

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