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JavaScript: What Is It, Popular Libraries, & Why Learn It

JavaScript is the number one programming language in the world and the most prevalent language in web development. About 97% of all websites in the world were built with JavaScript. That means that there are over 1.5 billion websites being powered by JavaScript.

JavaScript has come a long way in the past decade. It used to be used exclusively for the front end – also known as the client-side – which is the part of the website that users interact with. Nowadays, using APIs and frameworks, JavaScript can be used to create the back end – or server-side– of a website too. 

Nowadays, JavaScript can be used to build an entire full-stack website or web application and even native applications for mobile devices. This versatile and revolutionary addition to JavaScript is part of why it’s such a popular programming language. 

What is JavaScript?

Essentially, JavaScript is used to make websites interactive. JavaScript is a scripting language that allows developers to create dynamic and complex features on web pages. JavaScript is usually paired with HTML and CSS. Together, these programming languages make up a standard web technology stack. 

What does JavaScript do?

JavaScript works with HTML and CSS to build a dynamic website. HTML is the first layer of web development. It’s used to give the webpage structure, content, and meaning to search engines. CSS is the next layer, used to style the HTML content and adjust the visual layout of the webpage. Javascript, the third layer, enables dynamic content. 

It enables:

  • Timely content updates, automatically refreshing the page or a section of the page
  • Interactive maps
  • Animated 2D and 3D graphics
  • Store useful values inside variables
  • Add strings, or operations on a piece of content, to variables
  • Events-based responsive code, for example, executing a script based on a click
  • Display third-party widgets, like social media feeds, videos, or maps
  • Pop-ups
  • Drop-down menus 
  • Modal windows
  • Contact forms

JavaScript is even more versatile when you add its libraries, frameworks, and APIs. These prewritten packages of code help developers create web applications, mobile applications, desktop software, and websites more efficiently. 

What is a JavaScript Library?

A JavaScript library is a collection of prewritten code that was built to perform common tasks. Because libraries are usually well-tested before their release, they tend to be mostly stable and bug-free. Libraries often specialize in one specific use case such as a user interface. 

Libraries also usually reduce the amount of code that needs to be written which helps reduce bugs and make a website or application more efficient. Libraries are convenient ways for developers to avoid mistakes, build efficiently, and create reliable applications. 

What is an API?

Application Programming Interfaces (APIs) provide developers with prewritten chunks of code that act as a liaison between two technologies that don’t usually work together like the client-side or front end of a website and the server it is retrieving data from. You can think of an API like a key that provides access to a functionality that is difficult or impossible to achieve with JavaScript alone. 

There are two types of APIs: browser APIs and third-party APIs. Browser APIs are built into web browsers while third-party APIs power plug-ins and widgets for websites. Third-party APIs provide code that pulls information from elsewhere on the web. 

Browser APIs are able to expose data from the surrounding computer environment and are built into web browsers. Browser APIs enable things like popup windows, geographical location functions, animated graphics, multimedia players, and more.

Third-party APIs enable things like displaying automatically updating social media feeds like Twitter, embedding maps from a third party like Google Maps, or showing a media file from a streaming service like Spotify. 

What are JavaScript frameworks?

JavaScript frameworks have revolutionized the way people develop web applications. They’ve created incredibly efficient templates, bridged the gap between two technologies that couldn’t work together before, and even made it possible to build mobile apps with JavaScript! 

Frameworks provide reusable components for a website or application. You can think of frameworks like the blueprint for building an entire website. It provides structure, shows you which way to go using a preset application flow, and comes with premade tools that help you build each component faster than you could from scratch. 

The most popular JavaScript web frameworks include jQuery, React, React Native, Node.js, and Angular. Let’s take a closer look at each framework and the jargon that developers use to talk about them. 

Vanilla JavaScript

New JavaScript developers often ask, “What is the difference between Vanilla JavaScript and JavaScript?” The answer is that there is no difference between the two. Vanilla JavaScript simply means plain old JavaScript without libraries or frameworks. Native, standards-based, non-extended JavaScript. 


jQuery made JavaScript enormously popular. It was created to make it easier to use JavaScript in web development. jQuery simply takes common JavaScript tasks that usually require multiple lines of code to accomplish and packages them into methods that you can call with just one line of code. 

It simplifies many complicated aspects of JavaScript and makes nearly every part of web development more efficient. jQuery swears by the edict, “ write less, do more.” It’s free, open-source software that is independently maintained by its own foundation of volunteers. 


ReactJS, usually just called React, is a JavaScript library for building user interfaces. More simply put, React was developed to build the front end of a website. It’s the most popular framework of its kind.

React can be combined with other libraries to create entire applications for the web, mobile devices, or Windows desktop. It’s owned and maintained by Facebook but it remains open-source and free. 

React Native

React Native is essentially the JavaScript React framework for native applications. React Native can be used for cross-platform development. It enables front end developers to build native applications (apps) for Android and iOS using React – a JavaScript library. 

React Native is also open-source software created by Facebook. You can create platform-specific versions of each component in your React Native app so that you can build a complex, multi-platform app with one codebase, making debugging more centralized. 


Node.js allows web developers to develop a server-side component using JavaScript. This functionality means that a developer can build their entire site, front end to back end, using just JavaScript.

Node is free and runs on almost any platform. It works by leveraging an asynchronous, event-driven, non-blocking I/O model to make it lightweight and efficient. Node also offers npm, the world’s largest software registry with over 800,000 code packages for free. 


AngularJS is a structural framework for dynamic web applications. AngularJS enables the use of HTML as the template language and extends HTML’s syntax to express your application’s components clearly and succinctly. It’s perfect for building single-page applications. 

AnuglarJS was designed to reduce the amount of code developer’s usually have to write for an application like this. It’s free, open-source, and maintained by Google. This library has a vast support network and community. Millions of developers use Angular to build incredibly complex user interfaces. 


Other popular JavaScript frameworks include: 
  • Vue.js – pronounced like “view,” this framework is for building user interfaces from the ground up that can be implemented incrementally. 
  • Backbone.js – Backbone provides structure models for web applications and comes with a rich API collection. 
  • Ember.js – Ember.js provides templates, server APIs, and app structuring that enable the creation of complex, scalable, single-page application ecosystems.
  • MeteorJS – Meteor enables rapid prototyping and cross-platform coding. It’s based on Node.js.
  • Polymer JS – Polymer Project is a templating library with modern design principles. 
  • Webix – Webix is a toolkit created to build rich user interfaces and complex cross-platform web applications. 
  • Ext JS – Ext JS enables cross-platform web application development with common vanilla JavaScript scripts. It can be used to create components or single-page applications. 

Who uses JavaScript?

JavaScript is mostly used by web developers, software engineers, and mobile app developers. You can find JavaScript behind nearly any website. But even if you’re not sure you want to become a web developer, JavaScript is still worth learning. Proficiency will enable you to build websites from scratch, which is a useful skill in today’s economic climate! 

You could even build websites, web apps, games, or mobile apps without being a web developer full time. Some web developers work as a freelancer part-time, which keeps it fun while still providing an income. Others upskill through their work and use it to work their way up to a promotion. 

Whatever you choose, it pays to be a JavaScript expert. The best employers are using JavaScript. Everyone from local government to hotels, small businesses to banks is looking for JavaScript Developers. Seriously, you can find a JavaScript developer job in almost any industry.

Should I learn JavaScript?

Web development is constantly evolving. New tools are popping up consistently. It’s often hard to know where to start as an aspiring web developer. To stay relevant in today’s industry, knowing JavaScript is a must. 

Since its inception more than 25 years ago, JavaScript has taken over the web. That domination is unlikely to change anytime soon. It’s been the most commonly used programming language seven years in a row. 

JavaScript is one of the more beginner-friendly programming languages. There’s a huge community on Stack Overflow offering support for JavaScript, too. You’re sure to find support in this massive community of developers and hobbyists. 

JavaScript, along with its frameworks and APIs, can be used to create an entire full-stack web application and even mobile apps. This recent evolution that allowed JavaScript to bridge the gap between client-side and server-side has made skills in the language even more in-demand.

But with all of these libraries, frameworks, and APIs, do I actually need to learn vanilla JavaScript anymore? Yeah, you do. You might be able to get by in some ways but becoming knowledgeable about JavaScript and its syntax and relying on prewritten code. 

But you’ll have to patch that code together sometime, know which packages to use and when, and understand what each line of code is doing. If you want to become a web developer, you’ll most certainly need to be proficient in JavaScript and, beyond your first entry-level job, an expert. 

JavaScript is a versatile tool that is perfect for a web developer career. You’ll also find JavaScript in the toolbox of software engineers and mobile app developers. JavaScript can serve as the launching pad to a full-stack developer, software engineering, game developer, information security engineer, or machine learning job.

JavaScript supports object-oriented, imperative, and functional styles of programming which are all skills that transfer well to learning almost any other language used in web development such as Python. All of these roles require the most valuable skill of any JavaScript developer: problem-solving. 

Websites aren’t going anywhere anytime soon and neither are the problems that JavaScript developers solve, which makes learning JavaScript a no-brainer. There's no doubt that JavaScript will remain relevant and that there will be lucrative careers that rely on JavaScript for years to come.

With classes in-person or online and certificate programs that can be done even with a busy schedule, now is the time to start learning JavaScript! Upskill or change careers with our Software Engineering Immersive. 

Job Outlook for JavaScript Developers

JavaScript Developers are in high-demand, and likely will be for years to come. Over 70% of companies are hiring JavaSCript specialists. JavaScript developers are also well-paid. They earn $111,953 annually on average with plenty of room for upward mobility. 

There’s a sizable gap between the demand for JavaScript skills and the experts who can fill those positions. About 48% of employers are seeking JavaScript developers and only about 42% of new developers are proficient enough to fill those positions. 

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