WHAT IS JAVASCRIPT | Full Detail , Its Extra Knowledge

What is JavaScript?

JavaScript is a programming language that developers use to make interactive webpages. From refreshing social media feeds to displaying animations and interactive maps, JavaScript functions can improve a website’s user experience. As a client-side scripting language, it is one of the core technologies of the World Wide Web. For example, when browsing the internet, anytime you see an image carousel, a click-to-show dropdown menu, or dynamically changing element colors on a webpage, you see the effects of JavaScript.

What is JavaScript used for?

Historically, webpages were static, similar to pages in a book. A static page mainly displayed information in a fixed layout and did not do everything we now expect from a modern website. JavaScript emerged as a browser-side technology to make web applications more dynamic. Using JavaScript, browsers could respond to user interaction and change the content layout on the webpage.

As the language matured, JavaScript developers established libraries, frameworks, and programming practices and started using it outside of web browsers. Today, you can use JavaScript for both client-side and server-side development. We provide some common use cases in the following subsections:

Historically, webpages were static, similar to pages in a book. A static page mainly displayed information in a fixed layout and did not do everything we now expect from a modern website. JavaScript emerged as a browser-side technology to make web applications more dynamic. Using JavaScript, browsers could respond to user interaction and change the content layout on the webpage.

As the language matured, JavaScript developers established libraries, frameworks, and programming practices and started using it outside of web browsers. Today, you can use JavaScript for both client-side and server-side development. We provide some common use cases in the following subsections:

How does JavaScript work?

All programming languages work by translating English-like syntax into machine code, which the operating system then runs. JavaScript is broadly categorized as a scripting language, or an interpreted language. JavaScript code is interpreted—that is, directly translated into underlying machine language code by a JavaScript engine. With other programming languages, a compiler compiles the entire code into machine code in a separate step. Thus, all scripting languages are programming languages, but not all programming languages are scripting languages.

JavaScript engine

A JavaScript engine is a computer program that runs JavaScript code. The first JavaScript engines were mere interpreters, but all modern engines use just-in-time or runtime compilation to improve performance.

Client-side JavaScript

Client-side JavaScript refers to the way JavaScript works in your browser. In this case, the JavaScript engine is inside the browser code. All major web browsers come with their own built-in JavaScript engines.

Web application developers write JavaScript code with different functions associated with various events, such as a mouse click or mouse hover. These functions make changes to the HTML and CSS.

Here is an overview of how client-side JavaScript works:

1. The browser loads a webpage when you visit it.
2. During loading, the browser converts the page and all its elements, such as buttons, labels, and dropdown boxes, into a data structure called the Document Object Model (DOM).
3. The browser’s JavaScript engine converts the JavaScript code into bytecode. This code is an intermediary between the JavaScript syntax and the machine.
4. Different events, such as a mouse click on a button, trigger the execution of the associated JavaScript code block. The engine then interprets the bytecode and makes changes to the DOM.
5. The browser displays the new DOM.

Server-side JavaScript

Server-side JavaScript refers to the use of the coding language in back-end server logic. In this case, the JavaScript engine sits directly on the server. A server-side JavaScript function can access the database, perform different logical operations, and respond to various events triggered by the server’s operating system. The primary advantage of server-side scripting is that you can highly customize the website response based on your requirements, your access rights, and the information requests from the website.

Client-side vs. server-side

The word dynamic describes both client-side and server-side JavaScript. Dynamic behavior is the ability to update the webpage display to generate new content as required. The difference between client-side and server-side JavaScript lies in the way they generate new content. Server-side code dynamically generates new content by using application logic and modifying data from the database. Client-side JavaScript, on the other hand, dynamically generates new content inside the browser by using user-interface logic and modifying the webpage contents that are already on the client. The meaning is slightly different in the two contexts but is related, and both approaches work together to enhance the user experience.

Other than the implementation in dynamic features, another difference between the two JavaScript uses is in the resources the code can access. On the client side, the browser controls JavaScript’s runtime environment. The code can access only those resources which the browser permits it to access. For example, it cannot write content to your hard disk unless you click on a download button. On the other hand, server-side functions can access all the server machine’s resources as needed.

What are JavaScript libraries?

JavaScript libraries are collections of prewritten code snippets that web developers can reuse to perform standard JavaScript functions. JavaScript library code is plugged into the rest of the project’s code on an as-needed basis. If you think of the JavaScript application code as a house, JavaScript libraries are like ready-made furniture that developers can use to improve the functionality of the house.

The following are some common uses of JavaScript libraries:

Data visualization
Data visualization is crucial for users to view statistics, for example, in the admin panel, dashboard and performance metrics.

Libraries such as Chart.js, ApexCharts, and Algolia Places have built-in functions that you can use to create web applications that display data in charts and maps.

DOM manipulation

You can use libraries such as jQuery and Umbrella JS to make web development easy because they provide code for standard website functions such as menu animations, image galleries, buttons, lightboxes, and more.

Forms

All web development uses forms for website visitors to contact someone, order products, and register for events. Some JavaScript libraries, such as wForms, LiveValidation, Validanguage, and qForms, simplify form functions, including form validation, layout, conditions, and transformation.

Math and text functions

Many web applications have to solve mathematical equations and process dates, times, and text. Instead of sending all such requests to the server, handling some on the client side is more efficient. Web developers do this using JavaScript libraries such as Date.js, Sylvester, and JavaScript URL Library

What are JavaScript frameworks?

Like JavaScript libraries, JavaScript frameworks are a collection of prewritten code snippets that perform different functions and can be reused. However, whereas JavaScript libraries are a specialized tool for on-demand use, JavaScript frameworks are a complete tool set that helps shape and organize any web application. If you think of the JavaScript application code as a house, the JavaScript framework is the blueprint used to build the house.

Here are some example use cases for JavaScript frameworks:

Web and mobile application development

AngularJS is a framework that simplifies the development and testing of web applications, such as e-commerce applications, real-time applications, and video applications. React Native is another framework that supports natively rendered mobile application development for iOS and Android.

Responsive web development

Responsive websites give a consistent user experience across any device. For example, mobile and tablet screens are smaller than desktop and laptop screens. You want the website to display and present data accurately even on the smaller screen, without, for example, cutting off the ends of the website. Using frameworks such as Bootstrap and Ember.js, developers can benefit from responsive design and easily customize a website’s look and feel across different platforms.

Server-side application development

Node.js is a server-side, open-source JavaScript framework that runs JavaScript code outside a browser. Developers use this framework to build scalable, fast, and reliable network-based server-side applications. It can handle HTTP requests and data streams, support file systems, and manage multiple backend processes simultaneously.

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