Convert Java To Javascript: Java Explained

Table of Contents

Converting code from one programming language to another can be a daunting prospect. With two vastly different systems, how can you bridge the gap? That’s where this guide comes in. We’ll be looking at what makes up Java, what Javascript is, key concepts and guidelines for bridging the two languages, and more.

What is Java and What is Javascript?

Java is a high-level, object-oriented language used to develop software and apps. It’s had a long run in the programming world that started back in the mid-1990s, when researchers designed it with the intention of creating a platform-independent language that could be used across many different devices. As one of the most popular and longest-running computer languages out there, it’s used for apps and web-based software alike.

JavaScript, on the other hand, is a scripting language that’s typically used for single page applications and websites. Unlike Java, which is a “smart” language that follows instructions like a computer does, JavaScript follows instructions that most humans can understand. It’s used for transforming and updating content on a page on the fly, such as when a user wants to perform a search or type into a form field.

Differences Between Java and Javascript

Java and Java Script have their differences and similarities. Javas primary strength lies in its ability to cross platforms – you can take an application written in Java and run it on many different types of devices without issue. This isn’t the case with JavaScript – instead, JavaScript has built-in capabilities that allow it to interact directly with HTML, to render and change the look and feel of a web page in real time.

Java applications need to be compiled – they have to be translated into something the computer understands. JavaScript, however, doesn’t have to be compiled – it can simply be read by any web browser as it would understand the code.

Compilation RequiredYesNo
PlatformMultiple (Platform-independent)Web browsers
Primary UseSoftware and appsSingle page applications and websites

Key Concepts in Java

In order to understand how to convert Java code into JavaScript, it’s important to understand the key concepts behind Java. Here are some important features of the language you need to know.

  • Object Oriented Programming: Java is an object-oriented language, which means that developers can create classes for objects and instantiate those classes as objects. This makes code more modular, allowing easily reuseable sections of code.
  • Platform Independence: As mentioned above, Java is a platform-independent language, meaning it runs on many types of computers without having to recompile.
  • Memory Management: Because Java runs as bytecode on virtual machines, they have in-built garbage collection facilities that help with memory management.
  • API: Java has an expansive API (application programming interface) offering tons of built-in libraries that extend the core language.

Basic Syntax Rules of Java

In order to understand or write Java code, some basic syntax rules need to be followed. Here are some main ones:

  • Comments: Comments explain what your code is doing, they don’t execute. These are started using // or /* */.
  • Variables: Variables are containers for information. They must start with a letter or an underscore and only contain numbers, letters and underscores.
  • Semicolons: All lines of code must end with a semicolon.
  • String: Strings of characters are declared using “quotation marks”.
  • Case Sensitivity: All program components must be spelled correctly – if you write words incorrectly, it won’t be found!
  • Class definition: Classes must be defined with the keyword “class” followed by classname starting with a capital letter.


Let’s look at a simple Java code to print “Hello, World!” and its equivalent in JavaScript:


public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");


console.log("Hello, World!");

Common Pitfall in Conversion: Java’s strict type system can sometimes lead to issues when converting. Let’s say you have a Java function to add two numbers:


public static int addNumbers(int a, int b) {
    return a + b;

When converting to JavaScript, you need to be aware that JavaScript is dynamically typed:


function addNumbers(a, b) {
return a + b;

In the JavaScript version, a and b can be of any type, and JavaScript will try to “smartly” add them, potentially leading to unintended results. It’s crucial to ensure that the function is used correctly or to add type checks if needed.

Advantages and Disadvantages of Converting Java to Javascript

Taking Java code and converting it into JavaScript offers up several advantages and disadvantages. To begin, some advantages are:

  • Simplicity: JavaScript is known for its simplicity, so converting more complex Java code into it allows developers to simplify the code process.
  • Cost Efficiency: It may cost less to convert existing Java code than to create new JavaScript from scratch.
  • Faster Development Times: Converting existing code saves efforts rather than creating entire new pieces of code.

On the flip side, there are some disadvantages associated with converting Java to JavaScript:

  • Potential for Incompatibilities: Parts of the code may not work properly after conversion due to incompatibilities between the two languages.
  • Error Prone Code: Conversion may result in sloppy code leading to more bugs because of multiple conversions.
  • Additional Time Cost: It will take extra time to investigate potential incompatibilities between the two languages.

Common Issues When Converting Java to Javascript

When converting Java code into JavaScript there are several common issues. Some of them include:

  • Cross-browser compatibility issues: Different browsers interpret code differently, so make sure that your code works on different browsers.
  • Type handling differences between the two languages: Different type rules between Java and JavaScript can cause unexpected problems.
  • API differences between the two languages: Though many API functions in both languages are the same, there are cases where API functions may not have a direct equivalent or may require different parameters.
  • Object reference syntax differences: In Java, object references always use the dot notation whereas in JavaScript there is additional syntax like square brackets.
  • Event handling differences: Event handling in both languages are similar, but there are differences such as in how inline event handlers work.

Tips for Successfully Converting Java to Javascript

To ensure successful conversions when going from Java to JavaScript, here are some tips you should follow:

  • Check your code:: Before attempting the conversion make sure you’ve verified your existing code works properly. This will ensure that any unexpected behaviors are traceable to the conversion process rather than faulty existing code.
  • Understand your user scenarios:: Consider what devices/browsers your application will support in order to ensure proper conversion.
  • Choose existing libraries:: There are existing libraries and frameworks available for both languages that can either bridge the gap or make conversion easier; use them whenever possible.
  • Find help and advice from experts:: It may be beneficial to reach out to other developers familiar with both environments if you’re stuck on a particular issue. Still have questions? Ask an online expert!

Best Practices for Using Converted Java Code in Javascript Projects

Check for compatibility:: Make sure your code and libraries are compatible before jumping straight into using them in production apps.

Stick with references and imports only until safe:: Refrain from adding custom logic until you’ve double-checked everything works as expected.

Keep an eye on performance:: Since you won’t know exactly what your code will do in production, keep detailed logs and performance monitoring of your application as it runs.

Resources for Further Learning Java and Javascript

Stack Overflow: : Stack Overflow provides a platform for expert programmers to answer questions about coding topics related to both Java and JavaScript

W3Schools: : W3Schools provides a comprehensive list of tutorials and examples related to a wide variety of programming topics, including both Java and JavaScript.

Code Academy : Code Academy offers online tutorials and courses related to both languages starting at beginner levels.

YouTube : YouTube offers plenty of informative videos related to coding topics including tutorials on both languages.

Anand Das

Anand Das

Anand is Co-founder and CTO of Bito. He leads technical strategy and engineering, and is our biggest user! Formerly, Anand was CTO of Eyeota, a data company acquired by Dun & Bradstreet. He is co-founder of PubMatic, where he led the building of an ad exchange system that handles over 1 Trillion bids per day.

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