Both Java and JavaScript are commonly used web technologies. The similarities between their names often make beginners feel that JavaScript and Java are related. Java is an object-oriented, concurrent, and class-based, general purpose programming language, whereas JavaScript is an interpreted programming language. JavaScript is used widely as a client-side scripting language along with HTML and CSS, while Java is used by developer to build desktop GUI applications, websites and Android mobile apps. So it is important for programmers to understand the similarities and differences between the two popular technologies.

Similarities between Java and JavaScript

As a popular client-side scripting language, JavaScript makes it easier for programmers to enhance a website's user experience without putting additional load on server. Code written in this language can run on major web browsers. Likewise, Java applets can also run on most web browsers. But many programmers avoid these applets due to security and compatibility issues.

Java is used by developers for creating a wide variety of client-server web applications. The programming language runs smoothly on several web servers including Apache Tomcat, WebSphere and JBoss. Despite being used widely as a client-side scripting language, JavaScript can also be used on the server side through Node.js. The massive popularity of Node.js has resulted in the emergence of several web servers powered by JavaScript.

Both Java and JavaScript have many libraries and frameworks. These frameworks and libraries help developers to reduce coding time significantly. Likewise, the developers also have option to reuse the code shared by communities to avoid writing any additional code. The libraries and frameworks further contribute towards making the web technologies popular and current.

Differences between Java and JavaScript

Normally, Java code is written using an integrated development environment (IDE), and then compiled into bytecode. No human being can read or understand the bytecode. The bytecode can be read and understood only by the Java Virtual Machine (JVM). On the other hand, JavaScript code is directly executed by the web browsers as written by the programmers. However, many programmers nowadays use tools to reduce the size of JavaScript files, and hence make the code unreadable.

The bytecode makes Java code platform-independent. The programmers can run the same code on different platforms without making any modification. But JavaScript code is executed directly by the web browsers. So it can be impacted by browser-compatibility issues. Often developers have to use JQuery (ie, a JS library) to handle the browser incompatibility issues.

Java is a static typed language wherein the variable types are declared at the time of compilation. The variables can further accept values ​​permitted for the specific type. JavaScript, on the other hand is a dynamic typed language which allows programmers to declare variables with various value types including string, numeric and Boolean.

Working on a 100% object-oriented and class-based programming language, companies offering enterprise Java development services can use various OOP concepts to make the code reusable. This feature endears it to programmers who use it to create large and complex web applications. Despite supporting class and object, JavaScript is not fully object-oriented.

JavaScript supports closure in a manner similar to anonymous functions. The support enables programmers to pass a function as an argument to another function. But Java does not provide direct support to closures. The developers have option to use anonymous class to simulate closure. However, Java 8 supports lambda expressions to make it easier for developers to pass function as an argument to another function.

While creating websites, developers cannot use JavaScript independently. Nowadays programmer use JS along with HTML5 and CSS3 to create modern websites and web applications. But Java is can be used independently as a programming language for building a variety of applications. At present, the programming language is used widely for development of web applications and mobile apps.

On the whole, JavaScript is not part of the Java platform. The programmers can use each of them independently based on the requirements of individual projects. However, Java SE 8 is designed with Nashorn Javascript Engine, which enables developers to run dynamic JavaScript code natively on the Java Virtual Machine. So the developers now have option to call JavaScript functions directly from Java code.