Java vs. JavaScript: What's the Difference?

Though Java and JavaScript share half of a name, the two are far from the same. When looking at Java versus JavaScript syntax, you can see they look pretty different on the surface, and the differences go much deeper than that.

According to SlashData's annual survey, 2022 marks JavaScript’s 10th survey in a row rating as the most commonly used programming language. Java joins in as the fifth most popular programming language [1].

Let’s examine Java and JavaScript's differences, history, features, uses, advantages, and disadvantages.

What is the difference between Java and JavaScript?

When considering Java versus JavaScript, you’ll notice a few key differences. Java is a compiled language, meaning that you write code, then run it through a compiler and create bytecode. The bytecode is then run in a Java Virtual Machine (JVM), which is likely the software you have on your computer. JavaScript is an interpreted language. It doesn’t get compiled but is interpreted as the script runs. It's commonly used to create interactive websites. You’re reading this right now on a page running JavaScript.

What is Java?

Java launched with a “Write once, run anywhere” promise. Since its launch, it quickly became very popular for creating client and server-side applications. It has a similar syntax to C and C++. Still, it is easier to understand and has fewer low-level features because that functionality is handled automatically by the compiler and JVM.

Features of Java

Java has been around for some time, and as such, has developed a large community with a host of tools and educational content related to the language.

It’s on par or faster than most other modern compiled languages and much faster than interpreted languages, making it a good choice for robust native applications. Unlike JavaScript, Java is a multi-threaded language, meaning it can do multiple things simultaneously rather than wait for each task to finish before beginning the next one.

Java is very secure. It has private methods and variables built in, so there can be no unauthorized access to the underlying data and functionality. Additionally, the compiled app runs in a virtual machine which keeps itself separate from the underlying device it is running on.

What is Java used for?

Almost any desktop application, mobile application, game, website backend, or server can be created using Java, and it can even run machines. Wikipedia uses Java to execute its queries when you search on its website or app, and it even controls the systems in Mars rovers. Netflix, Google, Twitter, and several other big-name tech companies all use Java in some form to provide their services. 

Advantages of Java

There are many reasons why Java is one of the most widely used programming languages. Designed to be easy to use, Java is simpler to write and makes it easier to compile, debug and learn than other languages. It’s also object-oriented, meaning you can create modular programs and reusable code. One of Java’s most significant advantages is that it’s platform-independent. It’s able to move easily from one computer system to another.

Java is a robust language. Because it’s easy to use, platform independent, and has security features, it has become the language of choice for building the Internet of Things (IoT).

Disadvantages of Java

Though Java touts many excellent qualities, it lacks in performance. Java tends to run more slowly than languages like C and C++ and consumes a significant amount of memory. That extra memory is going to require more hardware to keep things running. More hardware means more money spent. Lastly, there is virtually no support for low-level programming. 

History of Java

James Gosling began developing Java in 1991. It was intended to be used for interactive television but at the time was too advanced for cable. Initially named Oak and then Green, it was finally given its official name of Java, after the type of coffee. Version 1.0 was released in 1996 under Sun Microsystems and became one of the most ubiquitously used technologies in the world. It is the foundation of the Android operating system and the language of the popular video game Minecraft.

What is JavaScript?

JavaScript has no direct relation to Java besides being used for web technologies. The name choice was a marketing move to encourage adoption.

Features of JavaScript

JavaScript has critical features that led to its widespread adoption. It runs live in the browser without having to compile beforehand, a process called just-in-time compilation. Every major web browser uses the language. It is responsible for many of the interactions you see on websites, like fetching new data without reloading the page, animations, checking forms for errors, chatting, posting comments, and much more.

What is JavaScript used for?

JavaScript is used by 97.8 per cent of all websites as of November 2022, according to W3Techs [2]. There are over 1.98 billion websites on the internet as of September 2022, according to First Site Guide [3]. That’s a lot of JavaScript. It can turn a static brochure-style website into a functioning application that lives in your web browser.

It’s not only for the front end, though. JavaScript can run in Node environments, allowing you to write JavaScript for the back end. It can perform routing, controller functions, an API service, or all of those things at once. Node enables you to have a fully JavaScript stack.

You can also make games in JavaScript. It is particularly suited for mobile and browser games, meaning you can make games for almost any device with a web browser. 

Advantages of JavaScript

The ability to run in a browser is a massive advantage for JavaScript. It’s one of the reasons that it has been the more popular language used in GitHub projects for several years in a row. Web browsers exist on a wide array of devices. All desktop computers, laptops, tablets, and smartphones have browsers, and many game consoles and smart TVs also have browsers.

When considering Java versus JavaScript for web development, JavaScript’s extreme versatility makes it an excellent choice. Being a full-stack engineer no longer means you must learn multiple languages. You have to know an array of ideas, patterns, and paradigms, but you only need one syntax to bring all of it together.

Because of its popularity and pervasiveness, there’s an abundance of educational material about JavaScript. You can find books, videos, courses, articles, and podcasts on just about every facet of the technology. It’s not difficult to find someone with the information you need to accomplish your goal.

Disadvantages of JavaScript

Even though every modern browser runs JavaScript, different browsers can sometimes behave a bit differently. Browsers have code that interprets the JavaScript at runtime called engines. Chrome and Brave, for example, use the V8 engine, while Firefox uses the SpiderMonkey engine. These engines often interpret the code in the same way, but there are instances where there is different behavior than you might expect. There’s always a workaround for consistent behavior and plenty of resources documenting the flaws and fixing them.

Some may say that JavaScript's dependence on the browser is a flaw. While the statement is somewhat true, as mentioned, it can now run in different environments with Node. And with tools like React Native, you can create stand-alone apps that run on the most popular environments, like Windows, Mac OS, iOS, and Android. There’s a learning curve you should be aware of, though.

Speed is another factor to consider. Programming languages are technically just doing complicated math very, very quickly. JavaScript is a high-level language, meaning it’s abstracted from the low-level workings of the computer it is running on. Reducing high-level programming calculations to low-level execution takes time. It’s not much time by human standards, but it will start to be noticeable over a few thousand functions and calculations.

History of JavaScript

JavaScript was created in 10 days by Netscape employee Brendan Eich. Released in September of 1995, the language was part of the beta for the Netscape Navigator web browser. It was first called Mocha, then LiveScript, and three months later the official name changed to JavaScript upon Navigator’s official release.

Learn to program on Coursera

Whether you're just getting started with programming or want to level up by learning a new language, you can learn at your own pace from leading companies and universities on Coursera. Learn the fundamentals with a beginner-friendly course like Object Oriented Programming in Java from Duke University or JavaScript for Beginners from the University of California, Davis.

If you already have some experience writing code, consider Full-Stack Web Development with React from the Hong Kong University of Science and Technology or Object Oriented Java Programming: Data Structures and Beyond from the University of California, San Diego, both offered on Coursera.