Introduction to JavaScript

What is JavaScript?

JavaScript is a programming language. JavaScript was initially created to make web pages interactive by adding dynamic behavior to the web page, animated graphics, reading cookies from a browser and interactive user actions.

Earlier only browsers contained a JS engine to execute JavaScript code, for example Chrome JavaScript engine called V8. This made JavaScript run only inside a browser.

What is Node.js?

To overcome dependency of JavaScript on browsers, Node.js came into picture which enables us to run JavaScript on a local machine instead of browsers.

Node.js is a runtime environment that executes JavaScript code outside of a browser. As a result, JavaScript can be used as a server side/ backend language as well as frontend/ client side language. It is built on Chrome JS engine V8.

Features of JavaScript :

• Lightweight interpreted programming language
• Client side as well as server side language
• Dynamically typed
• Simplicity : easy to learn and use

Why do testers need to learn JavaScript?

• One of the most popular programming languages today
• There are a lot of automation testing tools/ frameworks in the market that support programming in JavaScript like Cypress, NightWatch, WebdriverIO, Jasmine, Protractor etc.
• Strong community support for Node.js
• To automate Angular based web applications, single page websites etc.

According to a stackoverflow developer survey 2019 : JavaScript is one of the most popular languages today check here

What is NPM : Node Package Manager?

NPM is a Node Package Manager which allows us to share and reuse pieces of JS code. These pieces of JS code are called packages. Package manager is a concept common across different languages like Java, PHP, Python, Ruby etc.

NPM is the world’s largest software registry. The registry contains over 800,000 code packages.

Open source developers use NPM to share software projects. Many organizations also use NPM to manage private software  development.

JavaScript has two most popular package managers

• NPM (default package manager for JavaScript)
• Yarn

NPM consists of :

1. registry – NPM is a repository of open source JavaScript projects, open source and paid-for private packages
2. Command line client – Utility to publish, install packages and manage versions, dependencies

Installing NPM :

You have to install Node.js to get NPM installed on a local machine.

Download Node.js from official Node.js website : https://nodejs.org/en/download/

package.json

All NPM packages are defined in the package.json file. It lists the packages your project depends on. It also specifies versions of those packages.

Package.json file plays a vital role when you want to share your project with your team members. For example, if your project is using several dependencies then you don’t need to share your project along with these dependencies, you just need to share project with package.json

Creating a default ‘package.json’ file

To create a default package.json, use the npm init command with the –yes or -y flag.

1. On the command line, navigate to the root directory of your package.

cd /path/to/package

2. Run the following command:

npm init –yes