What is JavaScript (JS)? A beginner’s guide

Many web developers and programmers start off learning HTML, CSS, and JavaScript. If you are interested in building websites, you’ll need to know each of these languages. You’ll also need to know how they come together to create a functional website.

In this post, we’re focusing on JavaScript. We’ll cover everything you need to know from what is JavaScript to how JS is added to a website.

In the early days of the internet, websites were static. You only saw what was loaded onto the page, and you couldn’t interact with it. Websites were like printed posters that you viewed and accessed online.

The browser Netscape wanted to create a new language to make web pages more dynamic. In 1995, Brendan Eich, a computer programmer working at Netscape created JavaScript. He based JavaScript’s language and rules on existing programming languages Java and Scheme.

Not long after, the browser wars happened. Several browsers—Internet Explorer, Netscape, Firefox, Google Chrome, Safari, and others—competed to be the top browser for internet users. If you aren’t familiar with Netscape, it’s because it didn’t last long. It was replaced by competitors like Google Chrome, which dominates the market with 65% of users opting for it(opens new window).

However, JavaScript grew in popularity and became the standard for all web pages and browsers.

JavaScript is a programming language, one of the three—including HTML and CSS—that shapes the modern web. They are all necessary for web development. Before you can understand JavaScript—you need to know how it works with HTML and CSS. 

HTML code makes up the building blocks of the web. It structures web pages and tells a browser what to display. HTML can create page titles, headings, tables, hyperlinks, images, and more.

CSS tells the browser how to display the elements on a web page. For example, to add styling to your headings, you’ll need CSS to set the font size, colors, and so on. CSS identifies the HTML code you want to style and how to style it.

However, JavaScript makes a website function. Take an email sign-up form. HTML creates the structure of the form and button. CSS styles it. JavaScript makes the form and button work. It can tell the browser where to send the data and what to do after someone clicks the button, like take them to a thank you confirmation page.

JavaScript does much more than sign-up forms. It works on the client-side—what users interact with on a site—and server-side—what happens behind the scenes that users don’t access.

With only HTML and CSS, you’ll be able to view a website, but you won’t be able to do anything. JavaScript makes websites more than static elements on a page. With it, you can create dynamic, interactive elements, and more.

JavaScript powers the digital world. According to Stack Overflow’s 2022 developer survey(opens new window), JavaScript is the top programming language that developers use. It’s the tenth year in a row that JS has been at the top of the list.

All types of companies, from big brands to growing startups, need skilled JS developers. Because of its high demand, learning JS can open up thousands of high-paying job opportunities. At the time of writing, there are over 90,000 jobs on Indeed that are looking for JavaScript experience. With JS knowledge and experience, you can pursue web, backend, or mobile app development in a range of industries.

In most cases, JavaScript works together with browsers. All web browsers come with a runtime engine that reads and runs JavaScript. 

When a webpage is loaded, a browser runs the JavaScript code that comes with it. The code creates dynamic interactions, from making forms work (taking form input and making buttons functional) to creating in-browser games.

Modern browsers have a JavaScript engine, which is what runs the code and helps render the page. But how do you get your JS code onto a website?

The most common way to add JS to a website is to create a separate .js file that you’ll refer to within your HTML content. Typically you’ll instruct this in either the <head> tag to load ASAP or the <body> tag if you want it to load after the rest of the HTML above it.

You’ll insert the separate .js file into your HTML with this snippet of code:

<script src=[folder path to the file]></script>

This is the preferred method you’ll see across the internet, but it’s not the only method. You can also include regular JavaScript code into HTML with that same <script> tag. All you need to do is include the code you want to run between the opening and closing script tags.

Developers also use JavaScript with frameworks to create sites efficiently. Frameworks provide a foundation and tools for building websites and applications. Many websites have similar features, so frameworks use this to their advantage by compiling common scenarios, structures, and code into a library that developers can use.

It’s like getting a kit for building a house. The framework is the kit. Common JS frameworks include:

Instead of trying to start from scratch, you have a foundation ready to go. You also don’t need to memorize complicated blocks of code to create sophisticated JS functionality. Frameworks have libraries of pre-written code that you can repurpose for your development projects.

With frameworks like Meta’s React, developers build web pages entirely with JavaScript.

JavaScript extends beyond the web browser to power some of your favorite apps. Let’s take a look at what you can create as a developer using JS.

As we’ve discussed, websites and web applications are the most popular way that developers use JavaScript. Most developers build websites with JavaScript and frameworks like Node.js and React. If you want to become a Website or Frontend Developer, it’s a good idea to practice working with one or two JS frameworks.

You can also create full mobile apps that work natively on Android and iOS with frameworks like React Native(opens new window). While the React framework helps developers build websites, React Native is designed for mobile apps.

Cordova(opens new window) and Ionic(opens new window) are two lesser-known platforms you can leverage to easily build JavaScript mobile applications. These behave just like any other native mobile app would. However, they don’t require developers to learn a new language outside of JavaScript to create a mobile app. They also integrate into Node, React, Vue, and other JS frameworks.

Electron(opens new window) is another framework that specializes in helping JavaScript developers build desktop apps.

Tools like Electron make it possible for developers to create a web page that acts like a fully independent piece of software. Discord boasts over 150 million users every month, and it was built entirely using Electron.

With Node.js or Express.js, you can create web servers, APIs, and even a complete backend for websites. These frameworks give you a JavaScript runtime environment that runs outside a browser. A runtime environment is the software infrastructure that provides everything your code needs to run.

Google tags (gtag.js) is a real-world example of JavaScript working together with APIs and frameworks. If you aren’t familiar, with Google Tag Manager, you can use it to measure and track behavior on your site.

First, you need to add the tag to your site. It tracks events like clicks, purchases, page loading, and more. Then, you can view your site data in Analytics and other Google products. GTM uses JavaScript. When you edit your GTM configurations, it is writing JS code, although you may not realize it. You can also customize your tracking with some JavaScript knowledge.

Plenty of companies or products rely on JavaScript every day. Here are a few examples.

As we mentioned earlier, Discord was built from the ground up with Electron, a JavaScript Framework.

Both the web version and mobile app were created with React and React Native, respectively. Facebook’s parent company created the React frameworks. Instagram, the other social media company under Meta’s umbrella, also uses JavaScript for its web and mobile app.

The original streaming service has used React to create the web version of its platform. You can check out the Netflix team’s detailed blog post(opens new window) that shares why they chose React and how they use it.

Learning JavaScript can take between six to nine months. It can take longer depending on your coding experience. Most developers will recommend that you learn HTML and CSS first.

Luckily, because JS is everywhere on the internet, there are a plethora of resources to help you. Whether you want to know the basics or you want to polish and hone your craft, these tips and resources can help you get started.

Learning a programming language is a lot like learning a new language. You have to learn the syntax—the rules, structure, and meaning of the language—before you can practice and become fluent.

First, cover the basic components of JavaScript code–variables and functions. Then, you can get into more complex topics like decision-making and arrays.

Mozilla’s MDN(opens new window) is a free resource that many developers use every day. It has guides on HTML, CSS, JavaScript, and more. You’ll also find examples of JS code with explanations of how you can use it. If you forget the code snippet you need and Google it, MDN will most likely appear at the top of search results with the answer.

Writing code can be done in any text editor–Word, Notepad, or Google Docs. However, these aren’t designed with writing code in mind.

Instead, download and practice using a code editor. These are like text editors but they are designed for programming and have features that help you write better code, faster.

Microsoft’s Visual Studio Code(opens new window), also called VS Code, is one of the most popular, free code editors. You can also use Atom(opens new window) or Notepad++(opens new window).

Frameworks are popular with JavaScript, as they add a ton of valuable features and simplify the development process. Choose one or two frameworks to learn. If you are interested in working with a specific company, look up its job postings. Job descriptions will usually list the frameworks they would like potential candidates to know.

Study the framework’s documentation and create a few test projects to get familiar with how they work.

Coding requires problem-solving, and no two coding projects are exactly the same. As you’re learning, this can be a challenge. How do you practice for a wide variety of projects and needs?

You start building with JavaScript. Coding challenges help you build and apply your programming skills to real-life scenarios. For example, JavaScript30(opens new window) is a 30-day coding challenge. When you sign up, you’ll be sent 30 JavaScript challenges each day.

If you’re interested in a more structured learning approach with hands-on experience, apply for Multiverse’s Software Engineering apprenticeship. You’ll learn JavaScript and other programming languages during the program.

Multiverse apprenticeships are not only completely free, but you’ll get to learn on the job with a full-time role and salary. Apprentices also get access to one-on-one career coaching support, interview preparation, and more resources. You can begin the quick application process here.

Once you’re comfortable with your web development skills, the best way to show off your hard work is to build your own website. You can build it from scratch and prove to potential employers exactly what you’ve learned. Mix in case studies of your projects to show your progress and highlight your coding process.

There are no set rules on how to learn JavaScript, but consistency goes a long way. Take your time and keep practicing.