What Is JavaScript & What Is It Used For? A Basic Guide to JS

What Is JavaScript & What Is It Used For? A Basic Guide to JS


Each web page in your web site probably makes use of JavaScript.

Should you use Google Analytics, occasion monitoring, or show adverts, you’re already utilizing JavaScript.

However you may (and may) leverage it additional to create nice experiences on your customers. Earlier than you are able to do that, you must perceive what JavaScript is and what it’s used for.

What Is JavaScript?

JavaScript (JS) is a pc programming language used to make web sites and purposes dynamic and interactive.

It’s distinctive as a result of it will possibly run immediately in your browser, not simply on a server.

Together with hypertext markup language (HTML) and cascading fashion sheets (CSS), JavaScript is among the mostly used programming languages of the web.

Actually, 98.4% of all websites use JavaScript as of March 2023.

JavaScript, CSS, and HTML work collectively to make up the user-facing components of most web sites and on-line purposes.

Consider these coding languages because the elements of a home:

  • HTML is the muse of the home. It gives the fundamental structure, construction, and content material of an internet site.
  • CSS is the inside design. It gives design, fonts, colours, results, and different visible components. 
  • JavaScript is {the electrical} and plumbing programs. JS brings dynamism and interactivity to the web site. For instance, pop-ups, animations, video and social media embeds, drop-down menus, and lots of different web site elements are created utilizing JavaScript.
website components infographic

With out JavaScript, webpages could be largely static and boring.

JavaScript provides habits and interactivity. However it will possibly achieve this way more.

Historical past of JavaScript

Brendan Eich developed JavaScript in 1995 whereas working for Netscape.

Netscape sought to develop a scripting language that might assist make early variations of the World Vast Net extra dynamic.

JavaScript shortly gained reputation as builders realized its potential so as to add dynamism and interactivity to webpages. 

In 1996, Netscape submitted JavaScript to the European Pc Producers Affiliation (ECMA Worldwide), a corporation that goals to standardize the usage of info know-how programs.

This led to the creation of the ECMAScript standard, the formal specs for JavaScript. 

Its rising reputation has facilitated the event of libraries and frameworks, devoted JS engines comparable to V8 (which powers Chrome), and server-side environments.

Regardless of similarities in identify, JavaScript is fully totally different from Java.

Libraries vs. Frameworks

Libraries are collections of prewritten code that can be utilized to simply implement steadily used JavaScript duties.

Libraries result in sooner growth as a result of builders don’t want to jot down each line of code.

Frameworks are collections of libraries.

Consider libraries as instruments. And frameworks as totally loaded toolboxes.

Though a library can present code for a selected operate in your web site, a framework can present all of the code you must construct the web site. 

Frequent JavaScript libraries embrace jQuery and React. Frequent JavaScript frameworks embrace Vue.js, Node.js, and Angular.

What Is JavaScript Used For?

JavaScript is used to make dynamic web sites, net and cellular apps, video games, net servers, back-end infrastructures, and extra.

The next are the commonest makes use of of JavaScript.

Net Growth

JavaScript is mostly used to create dynamic, interactive web sites. 

Builders use JS so as to add animations, pop-up home windows, search bars, buttons, audio and video, chat widgets, and different interactive components to a webpage.

You can too use JS to supply real-time updates to a web page with out reloading it.

For instance, web sites with information tickers, inventory or crypto costs, or real-time product availability info usually use JavaScript so as to add this performance.

The entrance finish (user-facing facet) of many frequent web sites is constructed nearly fully on JavaScript, together with Google, Fb, Twitter, and Wikipedia. 

Net-Primarily based Video games and Functions

JavaScript is used to make most video games and purposes on the web. 

As a result of it runs immediately within the browser, JS permits customers to play video games and run purposes with out downloading further software program.

And since JavaScript is compiled into machine code because it’s executed (known as just-in-time compilation), easy capabilities and processes are carried out shortly.

This ends in a lot of dynamic, interactive utility. 

Different languages, comparable to C and C++, use ahead-of-time compilation. This implies the language is compiled into easier machine code earlier than it’s executed. 

Particularly for less complicated capabilities and processes, ahead-of-time compilation might be slower.

With JavaScript, builders can create something from easy arcade-style video games to sturdy multiplayer video games.

Moreover, interactive purposes like picture editors, venture administration instruments, chatbots comparable to ChatGPT, and calculators all use JavaScript. 

Even real-time communication purposes, comparable to Google Meet, Zoom, and Slack, can operate in-browser due to JS.

Server-Facet Programming

Server-side programming refers to code that runs on an online server to deal with requests from purchasers (comparable to net browsers) and return responses.

This enables builders to construct quick and scalable net purposes, work together with databases, construct utility programming interfaces (APIs), and facilitate real-time communication. 

For instance, server-side programming is what permits for dynamic pages like Fb’s newsfeed. 

If every publish, story, and standing replace have been constructed on particular person static pages, it could be extraordinarily inefficient and require tens of millions of pages. 

As a substitute, Fb makes use of fundamental HTML and CSS templates which are dynamically up to date with JavaScript as new info is available in. 

The identical idea applies to ecommerce web sites like Amazon. 

Amazon search outcomes and retailer pages are dynamically up to date utilizing JavaScript as gadgets promote out and others are added.

Cellular App Growth

JavaScript frameworks, comparable to React Native, Ionic, NativeScript, and Apache Cordova, allow builders to construct native and hybrid cellular apps for Android and iOS.

Fb, Google, Uber, and Instagram all use JavaScript to construct their cellular apps. 

JS is quick, environment friendly, and simple. And because of the reputation of the programming language, JavaScript builders are straightforward to search out.

Synthetic Intelligence

In recent times, builders have used JavaScript to construct purposes and programs that leverage synthetic intelligence.

You need to use JS libraries comparable to TensorFlow.js and Mind.js to construct and practice machine studying fashions for sentiment evaluation and advice programs. 

Different libraries can be utilized to course of and analyze human language for pure language processing (NLP) programs. 

Even chatbots, comparable to ChatGPT, are constructed utilizing JavaScript.

How Is JavaScript Completely different from Different Programming Languages?

JavaScript differs from different programming languages within the following methods:

It’s an Interpreted Language

This implies it may be executed immediately in a browser.

Different languages, like C, C++, and Java, are compiled languages and should be translated into machine code earlier than they are often executed.

It Makes use of Dynamic Typing

Dynamic typing means variable sorts are related to runtime values, not named or declared fields. 

This enables builders to jot down code sooner, as they don’t have to fret about specifying variable sorts. 

For instance, a developer may assign the variable “a” the worth of 100. The compiler will infer at runtime that “a” represents an integer. 

Nevertheless, this additionally means variable sorts may very well be misinterpreted as they’re run. This could trigger bugs and errors.

It’s Primarily Utilized in Consumer-Facet Execution

JavaScript is exclusive in that it’s mostly run within the consumer’s net browser. Not on a server.

This implies JavaScript can work together with the consumer, reply to consumer inputs, and dynamically replace the content material of the web page with no need to speak with a server. 

Different main languages, comparable to PHP and Ruby, are primarily used server-side. 

It’s Ubiquitous

In contrast to many pc programming languages which are confined to a handful of particular use instances, JavaScript is turning into a general-purpose language.

It’s supported by all main browsers.

It may be used each client-side and server-side.

And it may be used to develop web sites, cellular apps, and software program. 

What Are the Benefits and Limitations of JavaScript?

We’ve outlined the benefits and limitations of JavaScript beneath.

advantages and disadvantages of JavaScript


There are quite a few benefits to utilizing JavaScript:

  • It’s comparatively straightforward to study and use
  • It may be used for client-side and server-side, entrance finish and again finish
  • It gives dynamism and interactivity on web sites
  • On account of its reputation, there are various useful assets accessible
  • It runs on a number of platforms and units
  • It permits for cross-platform compatibility
  • It’s supported by all main net browsers
  • There are a lot of libraries, frameworks, and APIs accessible to facilitate duties
  • It’s quick for client-side and easy duties
  • It really works nicely in live performance with different programming languages


There are disadvantages and limitations of utilizing JavaScript:

  • It may be sluggish for computationally heavy duties
  • It comes with inherent safety considerations on account of entry to the shopper’s browser
  • Bugs might be tough to search out and resolve
  • Errors can stop JavaScript from rendering on an internet site
  • An excessive amount of JavaScript could trigger web site loading and efficiency points
  • Crawlers could have hassle crawling and analyzing JS content material
  • Browsers interpret JS in another way, which creates various experiences

How Does JavaScript Have an effect on Web site Efficiency?

Implementing JavaScript in your web site will negatively have an effect on its efficiency.

However if you use JS appropriately and sparsely, the advantages can counter the detrimental results on efficiency.

The extra code and scripts in your web page, the more serious the web page will carry out. 

Your consumer’s browser has to obtain, parse, and execute every JS script so as of HTML look. 

This consists of scripts comparable to Google Analytics, Google Tag Manager, Google Adverts, ImpactHero, and even net fonts.

Visible elements comparable to picture carousels and video embeds may improve web page loading time.

Advanced themes and plugins can even negatively have an effect on your web site efficiency.

By default, JavaScript parsing and execution takes place on the primary thread. Consider the primary thread as a queue of duties to be accomplished so as. 

You probably have too many JavaScript duties on the primary thread, it may delay the loading of different content material or photographs.

If necessary on-page components, comparable to your content material, load too slowly, it will possibly negatively have an effect on the consumer expertise and trigger them to bounce. 

This could harm your search engine marketing efforts, your site visitors, and, finally, your small business.

Moreover, not everybody has high-performance units and high-speed web connections.

Though pages could load shortly in your pc, they could not in your customers’ units. 

JavaScript impacts web site efficiency, however why does that matter?

Consumer Expertise

Including dynamism and interactivity to your webpages will enhance consumer expertise, however including an excessive amount of can have the other impact. 

An excessive amount of JavaScript causes your web site to load slowly—if in any respect.

Individuals don’t like ready. Particularly on the web.

In case your web site takes too lengthy to load, customers could also be pissed off, hit the again button, and depart on your rivals’ websites.

That is dangerous for enterprise. And dangerous on your search rating, too.

Core Net Vitals

Core Web Vitals are one other necessary consideration when evaluating your JavaScript use and web site efficiency.

Core Net Vitals are metrics Google developed to investigate an internet site’s efficiency and the expertise it gives. 

These metrics have an effect on your search rating. It’s necessary to observe them and guarantee your JavaScript isn’t inflicting points. 

Instruments like Semrush’s Site Audit and Google Search Console can determine JS-related points in your webpages. 

Easy methods to Use JavaScript on Your Web site

Should you’re one of many few web sites on the web not utilizing JavaScript, you may add it two methods:


You possibly can add JavaScript code to your web site by putting it immediately into the <head> of your webpage’s HTML supply code.

The JS code have to be enclosed in script tags, as proven beneath:

JS code enclosed in script tags


You can too add JavaScript to your web site by linking to an present JS file.

That is helpful if you need to add the identical code to a number of pages.

It’s additionally helpful when you’ve got a lot of code so as to add to the web page.

As a substitute of including tons of of strains of JavaScript to your HTML supply code, you may merely hyperlink to a separate file. 

JavaScript linking

Whatever the methodology you select, you have to make sure the code is enclosed in script tags on each web page you need it to work on.

Easy methods to Be taught JavaScript

To get essentially the most out of your web site with JavaScript, you’ll must take your schooling past the what and the why. 

We advocate the next assets and tutorials to get began:

JavaScript Points and Easy methods to Clear up Them

The chances are nearly limitless in the case of what you are able to do with JavaScript in your web site.

Nevertheless, to benefit from it, you have to guarantee your code is as polished as attainable. 

Semrush’s Site Audit tool might help guarantee your JavaScript is optimized and never hindering your web page efficiency. 

Unminified JavaScript

For JavaScript to work effectively and decrease detrimental web page efficiency results, the code have to be minified.

Unminified JavaScript comprises pointless strains and areas.

Eradicating these strains and areas can enhance web page load time with out sacrificing content material or performance.

The Web site Audit device can determine the place in your web site JavaScript must be minified.

Site Audit tool

First Enter Delay

First Input Delay (FID) refers back to the time it takes for the browser to reply after a consumer first interacts along with your web site (e.g., clicks a hyperlink).

FID is among the most necessary Core Net Vitals. And it will possibly have an effect on your search engine ranking.

You probably have FID points in your web site, JavaScript is a frequent and sure offender.

what causes poor FID

Fortunately, the Web site Audit device can determine First Enter Delay issues and what’s inflicting them.

Steadiness Is Key

JavaScript might help you present an unforgettable expertise on your customers.

However it will possibly additionally simply trigger web site efficiency points.

Steadiness is vital.

Strike a stability between consumer expertise and efficiency to optimize your web site.

Thankfully, the highly effective instruments accessible in Semrush’s Web site Audit might help you discover this stability and clear up points.

JavaScript FAQs

Listed here are some steadily requested questions and solutions about JavaScript:

What Is JavaScript and Why Is It used?

JavaScript is a pc programming language generally used so as to add dynamism and interactivity to webpages. It can be used to create cellular purposes and software program.

Builders use JavaScript as a result of it’s straightforward to study and use. It can be used throughout a number of platforms and units.

What Is JavaScript in Easy Phrases?

JavaScript is a pc programming language used to make web sites extra interactive.

What Is an Instance of JavaScript?

An instance of JavaScript is the code you place in your web site to put in Google Analytics.

Different examples embrace drop-down menus, interactive calendars, audio and video embeds, interactive maps, picture carousels, and show adverts.

Is JavaScript a Programming Language?

Sure, JavaScript is a programming or scripting language usually used to make web sites extra dynamic and interactive.

Are Java and JavaScript the Similar?

No, Java and JavaScript will not be the identical. They’re two distinct languages with totally different makes use of and functions. 

JavaScript was initially referred to as LiveScript, however its identify was modified earlier than its official launch. This was probably in an effort to capitalize on the recognition of Java on the time.


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