Category: Computer Programming

Node.js Tutorial Table of content What is Node.js? Why Learn Node.js? How to Install Node.js? Applications of Node.js Example of Node.js Application Prerequisites to Learn Node.js Getting Started with Node.js Frequently Asked Questions on Node.js PDF Version Quick Guide Resources Job Search Discussion Node.js is a powerful JavaScript runtime environment, built on Google Chrome”s V8 JavaScript Engine. Node.js is open-source and cross platform. What is Node.js? Node.js is not a programming language like Python, Java or C/C++. Node.js is a runtime, similar to Java virtual machine, that converts JavaScript code into machine code. It is , widely used by thousands of developers around the world to develop I/O intensive web applications like video streaming sites, single-page applications, and other web applications. With Node.js, it is possible to use JavaScript as a backend. With JavaScript already being a popular choice for frontend development, application development around MERN (MongoDB, Express, React and Node.js.) and MEAN (MongoDB, Express, Angular and Node.js) stacks is being increasingly employed by developers. Why Learn Node.js? Node.js can be used to full fill multiple purpose like server-side programming, build APIs, etc. Node.js is used for server-side programming with JavaScript. Hence, you can use a single programming language (JavaScript) for both front-end and back-end development. Node.js implements asynchronous execution of tasks in a single thread with async and await technique. This makes Node.js application significantly faster than multi-threaded applications. Node.js is being used to build command line applications, web applications, real-time chat applications, REST APIs etc. How to Install Node.js? Different operating systems required different steps to install Node.js, please follow the provided methods according to your installed operating system. Node.js Installation on Windows Node.js Installation on Linux – Ubuntu Applications of Node.js Node.js is used for building different type of applications. Some of the application types are listed below. Streaming applications: Node.js can easily handle real-time data streams, where it is required to download resources on-demand without overloading the server or the user’s local machine. Node.js can also provide quick data synchronization between the server and the client, which improves user experience by minimizing delays using the Node.js event loop. Single page apps: Node.js is an excellent choice for SPAs because of its capability to efficiently handle asynchronous calls and heavy input/output(I/O) workloads. Data driven SPAs built with Express.js are fast, efficient and robust. Realtime applications: Node.js is ideal for building lightweight real-time applications, like messaging apps interfaces, chatbots etc. Node.js has an event- based architecture, as a result has an excellent WebSocket support. It facilitates real-time two-way communication between the server and the client. APIs: At the heart of Node.js is JavaScript. Hence, it becomes handling JSON data is easier. You can therefore build REST based APIs with Node.js. These are some of the use cases of Node.js. However, its usage is not restricted to these types. Companies are increasingly employing Node.js for variety of applications. Example of Node.js Application To create a basic Hello World application in Node.js, save the following single line JavaScript as hello.js file. console.log(“Hello World”); Open a powershell (or command prompt) terminal in the folder in which hello.js file is present, and enter the following command. The “Hello World” message is displayed in the terminal. PS D:nodejs> node hello.js Hello World To create a “Hello, World!” web application using Node.js, save the following code as hello.js: http = require(”node:http”); listener = function (request, response) { // Send the HTTP header // HTTP Status: 200 : OK // Content Type: text/html response.writeHead(200, {”Content-Type”: ”text/html”}); // Send the response body as “Hello World” response.end(”<h2 style=”text-align: center;”>Hello World</h2>”); }; server = http.createServer(listener); server.listen(3000); // Console will print the message console.log(”Server running at http://127.0.0.1:3000/”); Run the above script from command line. C:nodejs> node hello.js Server running at http://127.0.0.1:3000/ The program starts the Node.js server on the localhost, and goes in the listen mode at port 3000. Now open a browser, and enter http://127.0.0.1:3000/ as the URL. The browser displays the Hello World message as desired. Prerequisites to Learn Node.js Before proceeding with this tutorial, you should have a basic understanding of JavaScript. As we are going to develop web-based applications using Node.js, it will be good if you have some understanding of other web technologies such as HTML, CSS, AJAX, etc. Getting Started with Node.js This tutorial is designed for software programmers who want to learn the Node.js and its architectural concepts from basics to advanced. This tutorial will give you enough understanding on all the necessary components of Node.js with suitable examples. Basics of Node.js Before going deep into nodejs you should familier with fundamentals of nodejs like environment setup, REPL terminal, NPM, Callbacks, Events, Objects, etc. Node.js Introduction Node.js Environment Setup Node.js First Application Node.js REPL Terminal Node.js Command Line Options Node.js Package Manager (NPM) Node.js Callbacks Concept Node.js Upload Files Node.js Send an Email Node.js Events Node.js Event Loop Node.js Event Emitter Node.js Debugger Node.js Global Objects Node.js Console Node.js Process Node.js File System Node.js Streams Node.js Scaling Application Node.js Packaging Node.js Modules Node.js modules provides a collection of functions that are used to perform different operations as per the requirements. All the improtant modules are listed below. Node.js Assert Module Node.js Buffer Module Node.js Console Module Node.js DNS Module Node.js OS Module Node.js Path Module Module Node.js Query String Tutorialspoint Node.js URL Tutorialspoint Node.js Utility Tutorialspoint Node.js V8 Tutorialspoint Node.js Jobs and Salary Node.js. is a popular tool for almost any kind of project. After Learning Node.js you can get job on different job profiles. Node.js Developer – Salary ranges in between ₹ 1.2 Lakhs to ₹ 12.6 Lakhs with an average annual salary of ₹ 5.7 Lakhs. Node.js Backend Developer – Salary ranges in between ₹ 1.2 Lakhs to ₹ 11.0 Lakhs with an average annual salary of ₹ 4.7 Lakhs. Frequently Asked Questions about Node.js Is Node.js Free to Use? Node.js is an open-source and cross-platform server framework. It is completely free to use on all the OS platforms – Windows, Linux, MacOS etc. Can Node.js

Node.js – NPM ”; Previous Next NPM − an acronym for Node Package Manager, refers to the Command line utility to install Node.js packages, perform version management and dependency management of Node.js packages. It also provides an online repository for node.js packages/modules which are searchable on https://www.npmjs.com/. A detailed documentation of NPM commands is also available on this link. If you are working with newer versions of Node.js (version 0.6.0 or later), the NPM utility is included with the Node.js binaries for all the OS platform bundles. Check the version of NPM in the command terminal − PS C:Usersmlath> npm -v 10.1.0 In case you have an older version of NPM, you need to update it to the latest version using the following command. npm install npm -g Note that YARN and PNPM tools are also available as alternatives for NPM. YARN installs packages more quickly and manage dependencies consistently across machines or in secure offline environments. PNPM (Performant NPM) is another fast and disk-space efficient package manager for Node.js packages. If your Node.js application depends on one or more external packages, they must be installed from NPM repository. NPM packages are installed in two modes either local or global. By default, a package is installed locally. Install Package Locally There is a simple syntax to install any Node.js module − npm install <Module Name> For example, following is the command to install a famous Node.js web framework module called express − npm install express Now you can use this module in your js file as following − var express = require(”express”); The local mode installation of a package refers to the package installation in node_modules directory lying in the folder where Node application is present. Locally deployed packages are accessible via require() method. Use –save at the end of the install command to add dependency entry into package.json of your application. The package.json file is a JSON file that is used to manage dependencies in Node.js projects. It contains information about the project, such as its name, version, and dependencies. The package.json file is used by the npm package manager to install and manage dependencies. The package.json file is typically located in the root directory of a Node.js project. It can be created by running the npm init command. Create a new folder for a new Node.js project, and run pnm init command inside it − PS D:nodejsnewnodeapp> npm init This utility will walk you through creating a package.json file. It only covers the most common items, and tries to guess sensible defaults. Use `npm install <pkg>` afterwards to install a package and save it as a dependency in the package.json file. Press ^C at any time to quit. package name: (newnodeapp) newnodeapp version: (1.0.0) description: Test Node.js App entry point: (index.js) test command: git repository: keywords: test, nodejs author: mvl license: (ISC) About to write to D:nodejsNewNodeApppackage.json − { “name”: “newnodeapp”, “version”: “1.0.0”, “description”: “Test Node.js App”, “main”: “index.js”, “scripts”: { “test”: “echo “Error: no test specified” && exit 1″ }, “keywords”: [ “test”, “nodejs” ], “author”: “mvl”, “license”: “ISC” } Now, if we install express package into this package locally in this project, use the following command, it also adds dependency entry into the package.json. D:nodejsnewnodeapp>npm install express –save The package.json file in this folder will be updated to − { “name”: “newnodeapp”, “version”: “1.0.0”, “description”: “Test Node.js App”, “main”: “index.js”, “scripts”: { “test”: “echo “Error: no test specified” && exit 1″ }, “keywords”: [ “test”, “nodejs” ], “author”: “mvl”, “license”: “ISC”, “dependencies”: { “express”: “^4.18.2″ } } The express package code will be placed inside the node_modules subfolder of the package folder. If you have already placed all the project dependencies in your package.json file, all of them will be installed at once by simply running npm install (without any package name in front of it) You can also use -save-dev flag in the npm install command to add the package as DevDepndency. –save-dev installs and adds the entry to the package.json file devDependencies –no-save installs but does not add the entry to the package.json file dependencies –save-optional installs and adds the entry to the package.json file optionalDependencies –no-optional will prevent optional dependencies from being installed Shorthands of the flags can also be used − -S: –save -D: –save-dev -O: –save-optional The difference between devDependencies and dependencies is that the former contains development tools, like a testing library, while the latter is bundled with the app in production. Install Package Globally Globally installed packages/dependencies are stored in system directory. Such dependencies can be used in CLI (Command Line Interface) function of any node.js but cannot be imported using require() in Node application directly. Now let”s try installing the express module using global installation. npm install express -g This will produce a similar result but the module will be installed globally. On Linux, the global packages are placed in /usr/lib/node_modules folder, while for Windows, the path is C:Usersyour-usernameAppDataRoamingnpmnode_modules. Update Package To update the package installed locally in your Node.js project, open the command prompt or terminal in your project project folder and write the following update command. npm update <package name> The following command will update the existing ExpressJS module to the latest version. PS D:nodejsnewnodeapp> npm update express up to date, audited 63 packages in 2s 11 packages are looking for funding run `npm fund` for details found 0 vulnerabilities Uninstall Packages To uninstall a package from your project”s dependencies, use the following command to remove a local package from your project. npm uninstall <package name> The following command will uninstall ExpressJS from the application. PS D:nodejsnewnodeapp> npm uninstall express removed 62 packages, and audited 1 package in 603ms found 0 vulnerabilities The package entry will also be removed from the list of dependencies in the package.json file. Print Page Previous Next Advertisements ”;

Node.js – Introduction ”; Previous Next What is Node.js? Node.js is a server-side runtime environment built on Google Chrome”s JavaScript Engine (V8 Engine). Node.js was developed by Ryan Dahl in 2009 and its latest version is v20.9.0. Node.js is a cross-platform (run on Windows, Linux, Unix, macOS, and more), open-source, back-end JavaScript runtime environment, that executes JavaScript code outside a web browser. The definition of Node.js as supplied by its official documentation is as follows − Node.js is a platform built on Chrome”s JavaScript runtime for easily building fast and scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. Node.js environment is event-driven and provides non-blocking I/O, that optimizes throughput and scalability in web applications. The OpenJS Foundation, facilitated by the Linux Foundation”s Collaborative Projects program, now handles the Node.js distributed development. Features of Node.js Following are some of the important features that make Node.js the first choice of software architects. Asynchronous and Event Driven − All APIs of Node.js library are asynchronous, that is, non-blocking. It essentially means a Node.js based server never waits for an API to return data. The server moves to the next API after calling it and a notification mechanism of Events of Node.js helps the server to get a response from the previous API call. Very Fast − Being built on Google Chrome”s V8 JavaScript Engine, Node.js library is very fast in code execution. Single Threaded but Highly Scalable − Node.js uses a single threaded model with event looping. Event mechanism helps the server to respond in a non-blocking way and makes the server highly scalable as opposed to traditional servers which create limited threads to handle requests. Node.js uses a single threaded program and the same program can provide service to a much larger number of requests than traditional servers like Apache HTTP Server. No Buffering − Node.js applications never buffer any data. These applications simply output the data in chunks. License − Node.js is released under the MIT license. The following diagram depicts some important parts of Node.js which we will discuss in detail in the subsequent chapters. Where to Use Node.js? Following are the areas where Node.js is proving itself as a perfect technology partner. I/O bound Applications Data Streaming Applications Data Intensive Real-time Applications (DIRT) JSON APIs based Applications Single Page Applications However, it is not advisable to use Node.js for CPU intensive applications. Node.js is primarily used to build network programs such as Web servers. However, you can build different types of applications such as command line applications, web applications, real-time chat applications, REST APIs etc. Thousands of open-source libraries for Node.js are available, most of them hosted on the npm website, npm is a package manager for the JavaScript programming language. A number web frameworks can be used to accelerate the development of applications. Some of the popular frameworks are Express.js, Feathers.js, Koa.js, Sails.js, Meteor, and many others. Number of IDEs such as Atom, JetBrains WebStorm, NetBeans, and Visual Studio Code support development of Node.js applications. Cloud-hosting platforms like Google Cloud Platform and AWS Elastic Beanstalk can be used to host Node.js applications. Print Page Previous Next Advertisements ”;

Node.js – Command Line Options ”; Previous Next Any JavaScript file (with .js extension) can be executed from the command prompt, using it as a command line option to the node executable. PS D:nodejs> node hello.js You can invoke the Node.js REPL by running node without any option. PS D:nodejs> node > In addition, there are many options that can be used in the node command line. To get the available command line options, use –help PS D:nodejs> node –help Some of the frequently used command line options (sometimes also called switches) are as follows − Display version PS D:nodejs> node -v v20.9.0 PS D:nodejs> node –version v20.9.0 Evaluate script PS D:nodejs> node –eval “console.log(123)” 123 PS D:nodejs> node -e “console.log(123)” 123 Show help PS D:nodejs> node -h PS D:nodejs> node –help Start REPL PS D:nodejs> node -i PS D:nodejs> node –interactive Load module PS D:nodejs> node -r “http” PS D:nodejs> node –require “http” You can pass arguments to the script to be executed from the command line. The arguments are stored in a an array process.argv. The 0th element in the array is the nide executable, first element is the javascript file, followed by the arguments passed. Save the following script as hello.js and run it from command line, pass a string argument to it from command line. const args = process.argv; console.log(args); const name = args[2]; console.log(“Hello,”, name); In the terminal, enter PS D:nodejs> node hello.js TutorialsPoint [ ”C:\nodejs\node.exe”, ”D:\nodejs\a.js”, ”TutorialsPoint” ] Hello, TutorialsPoint You can also accept input from the command line in Node.js. Node.js since version 7 provides the readline module for this purpose. The createInterface() method helps in setting input from a readable stream such as the process.stdin stream, which during the execution of a Node.js program is the terminal input, one line at a time. Save the following code as hello.js const readline = require(”readline”).createInterface({ input: process.stdin, output: process.stdout, }); readline.question(`What”s your name?`, name => { console.log(`Hi ${name}!`); readline.close(); }); The question() method shows the first parameter (a question) and waits for the user input. It calls the callback function once enter is pressed. Run from command line. Node runtime waits for user input and then echoes the output on the console. PS D:nodejs> node a.js What”s your name?TutorialsPoint Hi TutorialsPoint! You can also set environment variables from the command line. Assign the values to one or more variables before the node executable name. USER_ID=101 USER_NAME=admin node app.js Inside the script, the environment variables are available as the properties of the process.env object. process.env.USER_ID; // “101” process.env.USER_NAME; // “admin” Print Page Previous Next Advertisements ”;