What Is JavaScript, and What Are Its Uses?

30 November 2021
What Is JavaScript, and What Are Its Uses?

Are you new to web development? If so, you might be a little confused about the various languages used to develop websites. If you are confused about what JavaScript does that HTML or CSS cannot, read on. This post introduces the uses of Java Scripts. It also explains how JavaScript fits in the mix with the other web development technologies.

What Is JavaScript?

JavaScript, also called JScript or JS, is a text-based programming language used to create interactive elements on a website. The language can be used for both client-side and server-side scripting. JavaScript is also used for developing mobile apps and online games.

How Does Java Script Differ from HTML and CSS?

JavaScript is one of the three primary markup and programming languages used in web development. The other two are HTML (Hypertext Markup Language) and CSS (Cascading Style Sheets).

Other languages are used in web development, including Python, XML (eXtensible Markup Language), and Scala. But the fundamental building blocks of most websites are HTML, CSS, and JavaScript.

Hypertext Markup Language (HTML)

HTML provides the skeleton of a website. HTML uses tags to define content types. And, within those tags are the words of the content. So, an example of HTML code would be <h1> Hello World </h1>. In this example, the tag <H1> signifies that the text is a top-level heading, and Hello World is the text to be displayed in that heading.

Cascading Style Sheets (CCS)

HTML only provides the basic information on a web page. The formatting of that information is provided by cascading style sheets. CSS can be used to format a specific HTML tag, in which case it is called an inline style. CSS can be applied to an entire page of a website with an internal stylesheet. Or you can use an external stylesheet that will be applied to the whole website. The following code used in an external style sheet, for example, would make all h1 titles red; h1  color: red; .


JavaScript is the most powerful and complicated of the three fundamental web development technologies. Strictly speaking, HTML and CSS are not programming languages; they merely define the structure and style of content. JavaScript, on the other hand, is a programming language that performs dynamic functions. Like CSS, JavaScript can be applied inline, internal on a specific page, or external for the entire site.

What Are the Uses of JavaScript?

JavaScript is used for the interactive or dynamic elements on a website. JavaScript can be used for visual functions on the front end and to perform tasks at the back end.

Front End JavaScript Development

On the front need of a website, JavaScript can be used to create dynamic and interactive features. For example, a line of text could change color when a user’s mouse passes over that text. Or an image could change size when hovered over. Typical applications of JavaScript on the front end of a website include drop-down menus, displaying animations, tabbed content, and zooming in and out on an image.

Back End JavaScript Development

JavaScript can also be used to perform back-end or behind-the-scenes functions on a website. When used server-side, Java is usually used with the JavaScript runtime environment Node.js.

For example, JavaScript would typically be used to write data entered on a front-end form to the back-end database. JavaScript would also be used to process payments on an eCommerce site.

Mobile Application JavaScript Development

Used with frameworks like React Native, JavaScript can be used to develop mobile apps that will run on various operating systems. Before this development in the use of JavaScript, mobile apps had to be written in operating-system-specific languages. The Uber ridesharing app, for example, is powered by JavaScript.

Game JavaScript Development

JavaScript is not as powerful as some other programming languages. Even so, JavaScript is used to develop some of the simpler games, such as platform games. Two examples of JavaScript online games are Candy Crush Saga and Cookie Clicker.

Where can You See JavaScript in Use?

Wherever you see an interactive or dynamic element on a web page, there is likely to be JavaScript powering that element. And JavaScript can be seen in action on some of the world’s best-known websites. Many of these websites will have probably have used other languages, too. Still, JavaScript is used extensively in websites and mobile apps. Examples of well-known sites that use JavaScript are PayPal, Google, Netflix, and Amazon.

Why Do You Need JavaScript?

If HTML provides the skeleton of a website and CSS provides the skin, JavaScript brings the site to life. Indeed, without JavaScript, websites would consist purely of static pages with hyperlinks. And that is what the earliest websites were. Today, however, users expect much more from websites.

In modern website development, creating an excellent user experience is paramount. And a static website is not going to produce the best possible experience. So, creating user interactivity is essential, and JavaScript can provide that functionality.

JavaScript powers responsive websites, too. Combing JavaScript, HTML5 and CSS3, allows developers to create websites that look great across all devices and browsers. And those sites can be developed with a single code base.

There are alternatives to JavaScript, including CoffeeScript, Dart, and Kaffeine. However, JavaScript has become the industry standard and is relatively easy to learn. And JavaScript often simplifies the development of complex applications.


JavaScript is the technology used to create interactive elements on a website. And, unlike HTML and CSS, JavaScript is a programming language. JavaScript is also used to power websites’ back-end functions and develop mobile apps and some online games.

JavaScript is usually used with other third-party frameworks, such as Node.js, Angular, and React. These frameworks and other third-party tools generally contain functions that extend the functionality of JavaScript.

Approximately 95% of websites have some JavaScript in them. Indeed, JavaScript has become the standard language in the world of web programming. And, if you want to be a web developer, you will need to know CCS, HTML, and JavaScript, as these are the three primary technologies behind most websites.