What Is JavaScript? How It Works & What JavaScript Is Used For

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What is JavaScript? Commonly abbreviated JS, it is a popular scripting language created in 1995 that is used in front-end and back-end websites/apps and hybrid mobile apps.

It’s a client-side language that is used by 97.1% of all websites, making it the most popular programming language for web development by far.

In this post, we’ll cover more about what JavaScript is, Java vs. JavaScript, examples of what JavaScript is used for, how it works, what “client-side” actually means, the language’s pros and cons, and where to start learning it.

What Is JavaScript?

JavaScript is a flexible programming language that helps you make web pages more interactive, but also has tons of other use cases (which we’ll get into below).

Since it’s used by so many websites, JavaScript has been the most commonly used programming language for 8 years in a row according to a Stack Overflow survey.

💸 Naturally, its popularity makes it a highly in-demand language: 72% of companies are looking to hire JavaScript developers. As of April 2021, JavaScript developers made an average of $111,096/year in the US, so it’s a well-paid career as well.

javascript coding on laptop

Java vs JavaScript

In case you’re wondering, Java and JavaScript are completely different. JavaScript is an interpreted language, while Java is a compiled language (more on what that means later). Each has different runtime environments, libraries, etc. Learning one won’t necessarily make it easier to learn the other, so choose the one that best fits your tech goals!

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What Is JavaScript Used For?

JavaScript is mostly used for front-end development, but also back-end development sometimes. It’s commonly used alongside HTML/CSS, which are two of the best beginner-friendly languages!

JS can be used to build 👇 

  • Websites
  • Hybrid mobile applications that work on both Android and iOS
  • Desktop applications
  • Games
  • Interactive elements (e.g., calculators, quizzes)
  • Website functions like mouseover effects/click and drag boxes
  • User interfaces
  • And more! 

It can also be used in machine learning, robotics, and other interesting fields. 

Jobs that commonly use JS include: 

Why learn JavaScript? Basically, it opens up a variety of design and development careers, and enables you to build many different types of projects—JS is a very flexible language!

How Does JavaScript Work?

JavaScript is primarily a client-side language that executes in the browser. But what makes it unique is that it can also run server-side with platforms like Node.js.

Since browser scripting is JS’s most popular use, how exactly does this work? Websites typically contain embedded JavaScript code which only runs when a user actually visits that page.

javascript website on laptop

As we briefly mentioned in the Java vs. JavaScript section, JavaScript is an interpreted language, not a compiled language. 

Compiled languages like Java and C++ need to be compiled before they can run. The source code goes through a compiler, which translates the code into bytecode that the machine understands. 

However, since JavaScript is an interpreted language, this “compiling” step is completely bypassed. Instead, an interpreter in your browser (e.g., Chrome, Safari, FireFox) can “interpret” the JavaScript code and execute it.

⏰ For this reason, JS is often referred to as a “just-in-time” compiled programming language.

JavaScript Libraries and Frameworks

Another thing that makes JavaScript so appealing and popular among developers is that it comes with tons of libraries and frameworks that help you code more quickly, easily, and efficiently. With JS libraries and frameworks, there’s no need to reinvent the wheel.

javascript coding on desktop

JS libraries are reusable pieces of pre-written code that are used to perform common functions. Popular JS libraries include: 

  • jQuery
  • D3.js
  • React
  • TensorFlow.js ( a library for machine learning)

JS frameworks serve as a template/blueprint for building something with JavaScript; they consist of multiple libraries. Popular JS frameworks include: 

  • Angular
  • Bootstrap
  • Ember.js
  • Vue.js

💡 Fun fact: According to JavaScript.com, there are actually 1,444,231 JavaScript libraries and counting!

Read more about the different JS frameworks in this article about JS stacks.

Why Learn JavaScript? Advantages & Disadvantages

There’s no such thing as a perfect programming language, but when you’re choosing one to learn, why learn JavaScript? 

➕ Advantages of JS:

  • Little setup involved; you can start coding right in your browser
  • Runs in every web browser; no need to download anything extra
  • Runs on every device (e.g., mobile, desktop, tablet) so you can write cross-platform apps that work no matter what device the user has
  • It’s fast; client-side JavaScript can run immediately within a browser since it’s an interpreted language and doesn’t have to go through a compiler
  • Relatively easy to learn
  • Strong community; since it’s a very popular language, there are tons of resources, places to ask and answer questions, get help, etc. Stack Overflow currently has 2,199,603 questions on JavaScript alone!

➖ Disadvantages of JS:

  • Older browsers may not support JavaScript
  • Security: since JS code runs on a user’s computer and is viewable by the user, there’s a chance it can be exploited for malicious purposes
  • Each browser may interpret JS code slightly differently; users may see different things depending on what browser they’re using 

Overall, the pros of JavaScript easily outweigh the cons, especially if you’re looking for a relatively simple and powerful programming language to learn.

Get Started: Where to Learn JavaScript

There are generally no prerequisites required for you to jump in and start learning JavaScript. It can be a great first programming language, but it can also be a good one to pick up later in your coding journey. 

Here are a few courses to check out if you’re interested in learning more about JavaScript! ⬇️

Disclosure: I’m a proud affiliate for some of the resources mentioned in this article. If you buy a product through my links on this page, I may get a small commission for referring you. Thanks!

1. The Ultimate JavaScript Mastery Series by Code With Mosh

This 6 hour course is a good starting point for anyone who wants to master the fundamentals of JS.

2. Introduction to Javascript: The Basics on Coursera 

A 2h 10m long guided project course that teaches you how to create dynamic web pages with JavaScript.

3. JavaScript Web Projects: 20 Projects to Build Your Portfolio by Zero to Mastery 

Taught by industry experts who have worked with JavaScript in both Silicon Valley and Toronto, this course teaches you how to build 20 different JS projects, including a joke teller, a calculator, a MS Paint clone, and more.

Alternatively, check out my roundup of the best JavaScript courses.

Not ready to commit to a JavaScript paid course? Check out this post for places to learn JavaScript for free.

And finally, here are some examples of JavaScript projects you can build

Whether you’re looking to get a full-time web development job, build your own projects, or strike out on your own as a freelancer, learning JavaScript can be a great choice to help you reach your goals!