Java vs JavaScript: Everything You Need to Know by@R-Sharma

Java vs JavaScript: Everything You Need to Know

Ria Jaya Sharma HackerNoon profile picture

Ria Jaya Sharma

A Professional Writer and Blogger. 10 years of experience in the IT industry, article writing, and tech blogging.

Java vs JavaScript raises many questions. Are they the same? Is JavaScript an extended part of Java? Are they entirely different? Can I mix the code? Which one should I learn first? Which one is suitable for a startup web app?

After a detailed discussion with our dedicated Java developers I have articulated the following information that will answer all the questions.

"Java is to JavaScript as ham is to hamster." Baruch Sadogursky said in an interview with JAX London.

That used to be the best way to describe the relationship between these two.

However, standing at the end of 2019, the scenario is not the same. With passing years, both languages have evolved to fill different roles in programming and web development arena as a whole. Right now, they don’t compete with each other and also have marked a prominent appearance in the world of programming and web development.

Also Have a Look at: The Top JavaScript Frameworks For Front-End Development in 2020

Let’s Take a Closer Look — Java vs JavaScript

Java and JavaScript are written, assembled, executed differently, and even the capability of both languages vary significantly. Java is used in a wide range of server-side development, while JavaScript is best suited for developing client-side scripts for functions like interactivity and validation.

There are some more key differences that you will see further in this post. Before that, it is also important for you to know that programmers should learn these two languages to improve their coding repertoire. Also, you should hire full-stack Java programmers that can render Java-based web applications for your small, medium or large-size enterprise.


What Are The Major Differences? Java vs JavaScript

1. Compiled Language vs Interpreted Language

Java is a compiled language that runs on the virtual machine which is not readable by humans whereas JavaScript codes typically run on a JavaScript Engine in the same syntax it is written.

Creating a compiled program in Java requires several steps. Compiled languages are converted directly into machine code, and as a result, they tend to be faster than interpreted languages. In Java programming, you need to “rebuild” the program to make a change, whereas in JavaScript a program runs line by line and execute each command quickly.

JavaScript is an interpreted language that was once known to be slower than Java. But with the advancement of just-in-time compilation, there has been a significant improvement in the performance of JavaScript.

Advantages of Java for Programmers


Java is object-oriented programming that supports multithreading, so it has the capability to perform several tasks simultaneously. In Java, programs can be compiled into native code at compile time which usually tends to be faster than those translated at run time because of the overhead of the translation process.

Over the years, several open-source tools and IDEs have been created in Java such as Netbeans, and Eclipse.

Java offers various API’s that support the process of application development. Java APIs can be used as commands or methods of communication for various activities in programming such as XML parsing, networking, I/O, database connection, and much more.

Advantages of JavaScript for Programmers

JavaScript is an interpreted language that provides application developers some additional flexibility over Java implementations. JavaScript is relatively faster than Java because interpreters execute the source program code themselves.

JavaScript supports features such as dynamic typing and smaller executable program size. Unlike Java, the JavaScript language can be used in a huge variety of applications. JavaScript support many transpilers such as CoffeeScriptTypeScriptBabel (ES6 to ES5), and Elm.

The best thing about CoffeeScript is that it has simple functions that you can write as if you are writing a variable, see an example:

hello = (name = “Rebecca”)
console.log(“Hello, #{name}!”)
hello() # prints “Hello, Rebecca!”
hello(“Mary”) # prints “Hello, Mary!”

Whereas, TypeScript files use .ts extension to create a file and use the following code:

var client: string = ‘Mary’, // String
age: number = 26 // Numeric
function speak(name: string, age: number): void {
  console.log(name + “‘s age is “ + age);
speak(client, age);

Programmers can also write server-side code in JavaScript by using cross-platform such as Node.js that is designed particularly for the server-side runtime environment.

Although JavaScript is an interpreted language, it simplifies complex web application development for programmers by allowing them to use JavaScript libraries like AngularJS and ReactJS that can be used to create shadow DOM boundaries that make web browsers and applications deliver high-quality output.

Java vs JavaScript — Concurrency

Concurrency is handled very differently between Java and JavaScript.

The strength of Java class concurrency (java.lang.Thread) is that it allows developers to work with many threads that also help maintain parallel concurrency.


Whereas JavaScript runs on a single thread that responds to events when they occur during programming. JavaScript handles concurrency using a queue system that is called the “event loop” along with its features — heap, async/await, callbacks, event loop, and promises.

Async/Await in JavaScript — Works as a syntax over ‘Promises’ coding

Let’s imagine that you have a synchronize function that pulls some data out of the database, does some kind of processing, and then uploads the data somewhere in the cloud network.

In JavaScript

export class Synchronizer {
  // … other code elided …
  synchronize = notConcurrent(async () => {
    let data = await this.gatherData();
    // more processing
    await this.sendDataToServer(data);
// time A:
synchronizer.synchronize(); // => a promise
// a few seconds later, but before the sync has finished:
synchronizer.synchronize(); // => the same promise as before, no additional sync triggered


Promises behave like a sequential code and provide the sequence you need.

// This would be very difficult with callbacks
  .then(user => {
    return fetchJSON(`/users/${}/relatives`);
  .then(relativeIDs => {
    let promises = => {
      return fetchJSON(`users/${id};`);
    return Promise.all(promises);
  .then(relatives => console.log(friends));
  .then(user => {})
  .then(relativesIDs => {})
  .then(relatives => {})
  .catch(error => {
    console.error("And error occurred.");
function* generatorFunc() {
  let result = fetch("/users");
  // Pause execution by yielding
  yield result;
// Later something caused us to resume
console.log(`We're back!`);
function* generatorFunc() {
let result = fetch('/users');
// Pause execution by yielding
yield result;
// Later something caused us to resume
console.log(`We're back!`);

Java uses locks to protect certain parts of the code executed by several threads at the same time. Java maintains synchronization between locks and threads which is necessary to maintain reliable communication between threads.

For web app development projects, both Java and JavaScript works fine. If you ask for the best one, then Java works faster than JavaScript because of its thread to thread memory sharing which is faster than the JavaScript interprocess communication.

Java vs JavaScript — Class-Based or Prototype

Java is a class-based language that follows a blueprint and class-based relationship wherein all the properties are mentioned in a class and inherited by the instance of that class. Whereas, JavaScript is a prototypical language that allows all objects to inherit directly from the other objects of coding.

Java uses constructor functions:

class Foo {}
Typeof Foo // ‘function’

JavaScript uses the prototype chain to wire a child code

constructor.prototype’ to wire a parent code.

These steps are used to create parent/child hierarchies available in JavaScript OO design.

Why is inheritance important? Class inheritance is a “reuse code” mechanism that provides a way for different kind of objects to share code. Let’s look at an example where sayYourName() didn’t exist when the object was declared and was added at runtime.

// name property is added at declaration
var obj = {
  name: "Mary"
//this would throw an error - sayYourName() is not declared yet
// we add a new property at runtime
obj.sayYourName = function() {
  console.log("My name is " +;
// and now it works

There are many ways and patterns of creating objects and names in both Java and JavaScript. The best one is to use a prototypical way in JavaScript wherein objects should inherit from objects without any middleman.

Java vs JavaScript — Static or Dynamic Type of Checking


JavaScript is a scripting language that uses a dynamic form of coding and safety of codes verified at runtime. Java uses static type of checking where variables are checked at compile-time. In both the languages, it is important for a programmer to specify the integer type, string type, double type, etc. of the variable they create for coding.

Java static type checking is recommended for programmers as it helps you specify the type of error early in the application development. And, because this compiler knows what data types are being used they can code at a much faster rate. If you want to automate your JavaScript development process then rent a coder at affordable rates.

The benefit of JavaScript dynamic type of checking is that you are free to assign types of function that improves the programmer’s productivity.

Java vs JavaScript — Support Options

Oracle provides support to users facing problems with Java software. Users can access Oracle’s Premium Java SE Support service to resolve the issues related to the Java platform, Java components, Java standard edition, etc. Online forums are also available for the Java developers.

When talking about Java vs JavaScript we can’t ignore that there are some similarities between these two languages.

Support for back-end development — Both languages can be used on the server-side and support back-end development technologies such as Node.js, JBoss, and Apache.

Support for front-end development — Java and JavaScript both support front-end development and are easy to embed into HTML coding. Both languages provide access to techniques in coding such as encapsulation, polymorphism, and inheritance.

What Should You Choose For Your Next Project?

You should go for Java if you want a mobile application specifically for Android. Java is also best for building web and desktop apps that run on servers, enterprise-grade software, big data analytics, building server-side technologies like GlassFishJBoss, etc.

You should consider JavaScript if your project involves the need for developing single page applications (SPAs), server-side technologies like MongoDBExpress.jsNode.js, mobile app development on React Native or PhoneGap, etc.

Final Words on Java vs JavaScript

I hope you have a clearer picture of the differences between Java and JavaScript. Without a doubt, learning these two languages Java and JavaScript will make a programmer more productive and this will lead to the creation of enterprise-grade web applications, e-commerce development, and also helps in the development of Java software solutions.

Ria Jaya Sharma HackerNoon profile picture
by Ria Jaya Sharma @R-Sharma.A Professional Writer and Blogger. 10 years of experience in the IT industry, article writing, and tech blogging.
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