What is the difference between Java and JavaScript? This is one of the most common questions that web developers are often asked. JavaScript was initially called Mocha in May 1995, changed its name to LiveScript in September, and was finally given its current name in December when it received a license from Sun Microsystems - the creator of Java. Now, the two languages have become distinct in terms of their roles in web development and programming. This article will address both the similarities and differences between Java and JavaScript in further detail.

Defining Java

Java is a programming language designed to have as few implementation dependencies as possible. Java applications are compiled into bytecode that can run on implementations of the Java Virtual Machine (JVM), which acts as a bridge between source code and the 1s and 0s that the computer can understand. In short, Java can be run on any machine that has the JVM installed. This programming language mostly appears as a server-side language and the go-to programming language for mobile apps on the Android platform. Java is also relatively prominent on the front-end as a Java applet. However, this has become less popular because of security concerns.

Defining JavaScript

Along with HTML and CSS, JavaScript is one of the major core components of the web. It is a scripting language that usually runs in the browser and transforms web pages to become more interactive. JavaScript is rapidly becoming a server-side technology ever since the launch of Node.js back in 2009.

The Differences Between Java and JavaScript

By now, you should understand that Java and JavaScript are very different. Java was designed as a general-purpose programming language for developing standalone applications. JavaScript, on the other hand, is a scripting language designed for interfacing with web technologies, specifically HTML. In fact, when Java was first released in 1991, its main purpose was to program consumer electronics such as VCRs. JavaScript was meant to be used with Java as a client-side scripting language that can run in the browser without needing to be compiled. Here are some of the notable differences between the two languages:

1. Compiled Versus Interpreted

JavaScript is considered an interpreted scripting language, whereas Java is considered a compiled programing language. The distinction lies in the implementation. While Java is compiled into bytecode and run on a virtual device, JavaScript can be interpreted by a browser in the syntax it is written.

2. Static Versus Dynamic Type Checking

Java utilizes static type checking, in which the type of a variable is verified at compile-time, and the programmer has to spell out the type of any variable they create. However, JavaScript uses dynamic type checking, in which type safety is checked at runtime, and the programmer is not required to state the type of any variable they create. While there are both advantages and drawbacks for both paradigms, the static type checking is more advantageous when it comes to catching type errors early in development. Also, the compiler knows precisely what data types are being used, which is why code usually executes faster and consumes less memory. As for the dynamic type checking, the main advantage is programmer productivity, where you can assign types freely.

3. The Way Concurrency Is Handled

When it comes to handling the execution of many instruction sequences at the same time, Java and JavaScript have very different ways to do it. Java takes advantage of multiple threads to execute tasks in parallel. On the contrary, JavaScript, especially when it exists as Node.js in server-side applications, handles concurrency on a single main thread of execution through a queue system known as the event loop, as well as a forking system called Node Clustering. Both methods are fine for most use-cases. However, Java is typically faster as the thread to thread memory sharing is much quicker than interprocess communication (IPC).

4. Class-Based Versus Prototype-Based Inheritance

In Java, inheritance is class-based, referring to a top-down and hierarchical relationship by which properties are identified in a class and inherited by one of the members of that class. On the other hand, JavaScript follows prototype-based inheritance, meaning that all objects can inherit directly from other objects, and hierarchy is achieved by assigning an object as a prototype with a constructor function.

The Similarities Between Java and JavaScript

Despite their obvious differences, there are also some similarities between Java and JavaScript as well. Let’s take a look at the list down below:

1. Object-Oriented Programming (OOP)

Java and JavaScript require the developer to code in terms of objects and their associations to each other. This allows both languages access to techniques such as inheritance, encapsulation, and polymorphism.

2. Front-End Development

Both Java and JavaScript can be used in aspects of front-end development. While JavaScript can be embedded into HTML, Java can be used as a Java applet.

3. Back-End Development

The two languages can both be used on the server-side. Java has always been used to power back-end technologies such as JBoss, Apache, and WebSphere, while Node.js has become a launchpad for JavaScript-powered servers.