Java vs. JavaScript: How and Why They’re Different

When it comes to web development and programming, Java and JavaScript are two popular languages that come to mind.

At first glance, you might think they are the same thing, given their similar names. However, Java and JavaScript are fundamentally different languages, each with its own unique features and use cases.

In this article, we’ll explore the key differences between Java and JavaScript to help you gain a better understanding of these powerful languages.

0. Why Java and JavaScript have similar names

Java was developed by James Gosling at Sun Microsystems in 1995. It was designed as a platform-independent, object-oriented programming language with robust features for building complex applications.

JavaScript was created by Brendan Eich at Netscape Communications in 1995. Initially named LiveScript, it was renamed to JavaScript to capitalize on Java’s popularity. JavaScript was intended to make web pages more interactive and dynamic.

1. Platform

Java can run on any platform with a Java Virtual Machine (JVM). This flexibility has made Java a popular choice for developing cross-platform applications and server-side technologies.

It is typically used for large-scale projects and enterprise software development.

JavaScript is typically used for client side web browser code in web development, however its capabilities have expanded with libraries like Node.js, making it a popular choice for server side web applications.

2. Language Paradigm

One of the most significant differences between Java and JavaScript lies in their language paradigms. Java is a class-based, object-oriented programming language. It focuses on organizing code around classes and objects, which helps to create reusable and maintainable code structures.

For example, in Java:

// Define a class "Dog"
class Dog {
    private String name;
    private int age;

    // Constructor
    public Dog(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Getter methods
    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    // Method to make the dog bark
    public void bark() {
        System.out.println(name + " barks!");
    }
}

public class Main {
    public static void main(String[] args) {
        // Create a new Dog object and use its methods
        Dog myDog = new Dog("Buddy", 3);
        myDog.bark();
        System.out.println("My dog's name is " + myDog.getName() + " and it is " + myDog.getAge() + " years old.");
    }
}

On the other hand, JavaScript is a prototype-based, multi-paradigm language. It supports object-oriented, imperative, and functional programming styles, allowing developers to choose the approach that best fits their project requirements.
For example, in JavaScript

// Define a constructor function "Dog"
function Dog(name, age) {
    this.name = name;
    this.age = age;
}

// Add a "bark" method to the Dog prototype
Dog.prototype.bark = function() {
    console.log(this.name + " barks!");
};

// Create a new Dog object and use its methods
const myDog = new Dog("Buddy", 3);
myDog.bark();
console.log("My dog's name is " + myDog.name + " and it is " + myDog.age + " years old.");

3. Static vs Dynamic Typing

When comparing Java and JavaScript, it’s important to consider their typing systems.

Java is a statically-typed language, which means that variable types need to be explicitly defined at compile-time. This allows for early error detection and better code completion tools in development environments.

JavaScript is a dynamically-typed language. Variable types are determined during runtime, allowing for more flexibility in coding but also making it harder to catch type-related errors during development.

4. Compilation vs Interpretation

Java and JavaScript also differ in how they execute code.

Java code is first compiled into bytecode, which is then executed by the JVM. This approach allows for performance optimizations and error checking during compilation.

JavaScript is an interpreted language. The code is executed directly by the web browser (or another JavaScript engine).

Modern JavaScript engines, however, use Just-In-Time (JIT) compilation for performance optimizations.

5. Concurrency Model

Java supports multithreading and uses threads for concurrent execution of code. This enables developers to write high-performance applications that can efficiently utilize multiple processor cores.

JavaScript, however, employs a single-threaded, event-driven, non-blocking I/O model. Instead of using multiple threads, JavaScript handles multiple tasks concurrently using asynchronous callbacks and event loops. This approach makes JavaScript suitable for handling a high volume of I/O-bound operations without the added complexity of managing multiple threads.

TL;DR

Java and JavaScript, despite their similar names, have distinct characteristics and use cases.

#	Difference	Java	JavaScript
0	Naming Origin	Developed by James Gosling	Created by Brendan Eich
1	Platform	Runs on Java Virtual Machine (JVM)	Web browsers (client side) & Node.js (server side)
2	Language Paradigm	Class-based, object-oriented	Prototype-based, multi-paradigm
3	Typing System	Statically-typed	Dynamically-typed
4	Code Execution	Compiled into bytecode, then executed by JVM	Interpreted language (JIT compilation)
5	Concurrency Model	Multithreading	Single-threaded, event-driven, non-blocking I/O