What Is JavaScript? The Powerhouse Behind Dynamic Web Experiences

What Is Javascript

I don’t think we truly remember just how uninteresting websites were before JavaScript was a thing. They were basically online brochures — just text and images sitting there. You really had to fall in love with the fonts and colors, because that’s all there was.

You couldn’t click a button to update content instantly. There were no drop-down menus. No interactive forms or animations. That was out of the question. Then came JavaScript.

JavaScript is a programming language that makes websites interactive.

It changed everything for the better. Today, interactivity is just a fraction of what JavaScript can do.

Key Features of JavaScript

JavaScript is the world’s most used programming language among developers. Looking at its features will make you understand why it’s so popular.

Client-Side Scripting

By “client-side,” I mean the front side of the website. You, the viewer, are the client in this case. The opposite of the client side is the server side. I’ll go into details about the server side later.

Javascript definition infographic

Since JavaScript can live on the client’s side, it makes web pages really fun to interact with. That brings me to my next point.

Event-Driven Programming

Any interaction with a webpage is called an event. You click on a button; that’s an event. You scroll up the page; that’s another event. You exit that page, still an event.

It’s JavaScript’s job to listen and respond to these events.

JavaScript responds to events per the code’s instructions. So next time a website thanks you for filling out a form or completing a transaction, that’s JavaScript responding to an event.

Dynamic Typing and Prototypal Inheritance

JavaScript code is dynamic and can take many forms while being executed. This means you don’t have to explicitly define your variable type when you assign it. For example, you can assign a variable to a number and change it to a string without consequence.

Dynamic typing in javascript infographic

Then there’s prototypal inheritance. This is how JavaScript lets objects share properties with each other. It’s unlike Java, where there are very specific rules for inheritance.

Asynchronous Programming

Don’t let this phrase scare you. All it means is that JavaScript can multitask. Or rather, as I like to think of it, has no patience.

JavaScript doesn’t have to wait for other tasks to finish before running the next. Take YouTube as an example. For starters, it’s heavily JavaScript-ed.

While you’re watching a funny cat video, YouTube already knows what video to recommend to you after you’re done watching Fluffy knock over the Christmas tree. That’s asynchronous programming in action. But for it to work, JavaScript uses tools like callbacks, promises, and async/await.

A callback is similar to a note or text message. JavaScript knows it needs to make a phone call to the server, but then it decides to shelve that idea for later. So it decides to leave a message like:

“Hey, call me back when you’re done with your class. I’ll go ahead with my other errands for the day.” That shows just how impatient JavaScript is. It simply cannot wait in line for the server to pick up the call!

It’s the same thing with promises. A “promise” is the server telling JavaScript that it’ll respond to a request when the right time comes.

The server can either decide to honor the callback request or reject it. If honored, the callback request is considered resolved. And because we don’t write ordinary sentences in JavaScript, we use keywords like async/await instead.

Async is what makes a function asynchronous. Await tells JavaScript to pause the function before another task is completed. Look at the JavaScript code below as an example:

JavaScript async await example

Now let me explain what’s happening in the code above.

The fetchData function is marked as async. This immediately tells the server what kind of function it is. The server, in this case, already knows what to expect from async.

The await tells the function to wait until after it receives the API data from the server.

History of JavaScript

JavaScript’s history is pretty interesting. Here’s an overview.

Creation and Early Development

JavaScript was created in 1995 by Brendan Eich, an American computer programmer, while working at Netscape. From the very beginning, he wanted to make web pages interactive.

After its completion, this language was originally named LiveScript. Bear in mind that no one had ever heard of the name “JavaScript” at the time. That is despite the fact that the dot-com era had just started.

At the time, Java ruled the streets. Trying to promote JavaScript would be like bringing sand to the beach. So the folks at Netscape came up with this brilliant idea to rename LiveScript to JavaScript. And it worked like magic.

Many developers thought JavaScript was related to Java — though it wasn’t.

Out of curiosity, more and more developers started learning about this new language. And as they say, the rest is history. As I write this, no other programming language in the world has more users than JavaScript.

Netscape knew it had something special in its hands. It just needed to figure out how to get developers on board. And it did exactly that with a simple yet well-thought-of name change.

Evolution of JavaScript

JavaScript had become so popular, but there was no standard set of rules on how to write it. For a moment, that was fun. You didn’t have to follow any rules. If the code worked on your browser, that was more than enough.

Things started to change when developers realized that different browsers process code differently. Take the code below as an example:

innerText example

In Internet Explorer, this code worked just fine. When used in Firefox or Netscape, it expected textContent instead of innerText.

That alone was enough to cause problems.

Ecma International, a group that sets standards for technology, created ECMAScript, a type of guidebook for JavaScript users.

Over the years, Ecma International has released different versions of the ECMAScript guidebook. The table below breaks down how JavaScript has evolved since its inception about three decades ago and some key updates made.

Evolution of JavaScript

ECMAScript VersionYear ReleasedKey Features Added
ES52009Added JSON support, “strict mode,” and more
ES6 (ES2015)2015Introduced let/const, arrow functions, promises, and modules
ES7 (ES2016)2016Array includes method, exponential operator
ES8 (ES2017)2017Added async, await, object.entries, and object.values
ES9 (ES2018)2018Rest/spread properties, asynchronous iteration

Next time you hear about ES5, ES6, or anything along those lines, they’re just referring to updated versions of the original ECMAScript rulebook.

The Rise of JavaScript Libraries and Frameworks

Creating JavaScript was a huge milestone. But that wasn’t the end of the journey.

As developers became more creative and websites more complex, it was necessary to develop building blocks that would make JavaScript web development much easier. They named these building blocks JavaScript libraries and frameworks.

One popular library, named jQuery, simplified tasks such as web interface (DOM) manipulation and event handling. Shortly after, other full-fledged frameworks like Angular, React, and Vue.js entered the scene. As a result, developing large-scale web applications with better performance and maintainability became much easier.

JavaScript in Web Development

In web development, you’ll find JavaScript both at the front end and back end. Here’s what to expect.

Role of JavaScript in Frontend Development

Let’s first define frontend development. The front end is basically the front side of a website or application, like what you’re looking at right now. Here, you’ll find text, images, buttons, graphics, and other features that make you want to interact with a website or app.

In frontend development, we use JavaScript and its libraries and frameworks to create interactive user interfaces.

Examples include:

  • React
  • Angular
  • Vue.js
  • jQuery
  • Svelte
  • Backbone.js

X, formerly Twitter, is perhaps the best example of a frontend JavaScript library in action. It uses React components to load content without refreshing the entire page.

Role of JavaScript in Backend Development

The backend side of a website or application is more hidden (and for good reasons). Think of it like the technical components in the back of your television — it’s covered in plastic to protect it from dust and being tampered with.

In web development, we use JavaScript to build server-side applications. That’s because it can handle data, databases, and servers and simultaneously perform multiple tasks like user authentication or data storage.

Full-Stack Development

By now, you should have an idea of what full-stack web development is all about. That’s what you get when you combine back-end and frontend development.

Here, you decide the combination you want to build your website or application with. For perspective, I’m a MEAN web developer.

Side note: I’m talking about a tech stack; I’m not a rude web developer.

In full-stack web development, MEAN stands for MongoDB, Express, Angular, and Node.js. Other developers specialize in MERN stack development. That’s short form for MongoDB, Express, React, and Node.js.

With these stacks, you can work on both the user interface and the server-side logic using JavaScript.

Tools and Ecosystem

JavaScript needs certain tools and ecosystems to function correctly. Here are some examples.

Development Tools

Web developers use text editors like Visual Studio Code or Sublime Text to write JavaScript.

Development Tools icon

Others may opt for more advanced Integrated Development Environments (IDEs) such as WebStorm to write their code.

But text editors alone are not enough. They say JavaScript is one percent coding and 99% debugging. Without debugging tools, you’d lose your mind trying to find and fix errors.

Most people use browser developer tools (like Chrome DevTools) to track down issues.

These tools can inspect elements and analyze performance, all in real-time.

Package Managers

Remember when we talked about JavaScript libraries? You’ll need to set up a system to manage them.

Take your local community library as an example. There’s usually a staff member at the front desk to offer assistance when needed.

In JavaScript, that’s the work of package managers like Node Package Manager or Yarn. We use them to install, update, and manage external code libraries.

Frameworks and Libraries

I’ve talked about libraries and frameworks before, but let’s circle back to the topic one more time. We’ve seen that React, Angular, and Vue.js are the most widely used for building user interfaces.

Frameworks and Libraries icon

But what’s the difference between a JavaScript library and a framework?

A framework is more of a basic structure. I like to think of it like a wooden frame for a house, something that provides the bones for the drywall, insulation, and roof. You just need to customize and complete it.

A library is a specific functionality used within an app. Since I used a real-life library as an example earlier, I’ll try to stay consistent with my analogy.

Let’s say you’re building a bookshelf in an actual library. It could be your home library, or maybe you’re an interior designer hired to upgrade your local community library.

While you could build a bookshelf from scratch, you instead decide to buy prefabricated shelves from IKEA. The parts come ready to go with the tools you need to assemble them. You have all the wood, screws, and a basic plan.

In JavaScript, a library is pre-written code that you can use over and over again to make development faster and more streamlined.

Does that make sense? If not, the table below will make things clearer.

Frameworks vs. Libraries

FeatureFramework (Angular)Library (React, Vue.js)
StructureComplete app structureFocused on specific tasks
FlexibilityLess flexible, opinionatedMore flexible, easy to integrate
Learning curveSteeperEasier to learn

Now let’s talk about how JavaScript has impacted modern technology.

JavaScript and Modern Technologies

JavaScript was invented because someone didn’t like how boring websites looked back then. But then it became a powerful and important part of modern technology.

JavaScript in Mobile App Development

In mobile app development, for example, JavaScript returns to the scene through frameworks like React Native and Ionic. Web developers use these frameworks to write mobile applications and then deploy them on both iOS and Android.

Because React and Ionic are frameworks, they make developing mobile applications much faster. After development, it’s even easier to maintain these applications.

One more thing: these JavaScript frameworks boast a huge community of developers. You can always reach out to this community if you need help figuring things out.

JavaScript and WebAssembly

I have a secret: Laziness is an important skill in web development. They don’t teach you that at a coding boot camp!

It’s one of those things you learn by working tirelessly and getting minimal results. Then you pause for a moment and think:

“Hmmm, how about I try to work smarter instead of harder?”

Here’s what I mean:

Picture a situation where your boss wants you to develop online video editing software with JavaScript. If you’re a hard worker, you’ll write JavaScript from scratch. The app might function, but your brain likely won’t after that.

A lazy developer will use WebAssembly, a low-level code that runs alongside JavaScript in web browsers, to help simplify the process.

WebAssembly screenshot
Visit WebAssembly.org to get started.

WebAssembly is like a friend that helps JavaScript work faster when handling demanding tasks. It does the heavy lifting, and that frees up JavaScript to focus on the easier stuff. For example, as it handles video editing, JavaScript makes sure that the buttons work.

The Rise of Serverless Architecture

Let’s talk about serverless computing. For starters, it is exactly what it sounds like. You don’t need to stress about managing servers. It’s not the early 2000s anymore. Once you’ve written your code, you deploy it to the cloud and fetch it anytime you want to.

Platforms like AWS Lambda, Google Cloud Functions, IBM Cloud Engine, and Microsoft Azure Functions are good examples of serverless environments.

Challenges and Limitations

Don’t let my praise for JavaScript make you think it’s the perfect programming language. In fact, there’s no such thing as a perfect programming language. JavaScript comes with some challenges you need to know about.

Security Issues

One of the biggest challenges of using JavaScript is the issue of common security vulnerabilities like Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF).

You’ve probably experienced XSS before; you just didn’t know what it was. This is a scenario where attackers inject malicious scripts into a website. These scripts will then redirect you to a website that steals your information.

CSRF is even more malicious. If you fall for it, the consequences can be pretty serious. It tricks you into performing certain actions on a website, like clicking on a link, submitting a form, or even completing a transaction.

Even worse, it knows how and when to attack. You don’t see it coming.

Let’s say you want to log in to your online bank account. The attacker will hang around until you’ve successfully logged in. If you visit a malicious page while logged in to your online banking platform, that page can send a request to the banking site in the background.

Something like, “Transfer X amount of cash to this new account.”

Since you’re still authenticated, the online banking platform will assume that the request is legitimate. It’ll then process it. Now you know why your bank automatically logs you out after a specific period of inactivity.

Granted, security threats will continue to exist even as JavaScript evolves. The best thing to do to protect your website or application is to follow best practices. I’m talking about things like setting up input validation, sanitizing user data, and using security headers to protect your code.

Performance Concerns

JavaScript is sometimes a pain to work with. Because it runs in the browser, it can slow down a website if not properly optimized. But there’s always a way to fix performance issues: code minimization, lazy loading, and asynchronous operations.

That’s the beauty of programming. It’s like an endless cycle of solving problems, creating even more, and solving them again. And if you’re lucky, you get paid for it.

Browser Compatibility

I gave an example of how JavaScript can behave differently depending on the browser. That’s not so common nowadays due to ECMA’s standardization. However, whether or not your code will work as it should depends on many other factors. It’s not just the mere fact that you’ve used JavaScript.

For instance, the way older versions of Internet Explorer handle event listeners (attachEvent vs. addEventListener) differs from modern browsers. To solve this problem, you can use tools like Babel and Polyfills.

Built to Interact, Here to Impact

JavaScript went from being a fresh-faced interactive programming language to becoming one of the most important building blocks of the modern internet. And I don’t mean only at the browser level. Most mobile applications and software today run on JavaScript.

Where vanilla JavaScript is not involved, you’ll most likely find its library or framework. That shows you just how important this programming language is.