Java vs. JavaScript: What’s the Difference?

Java and Javascript, both may sound similar to one’s ears because of the word ‘java’, but these two are nothing alike. Although both Java and Javascript are used for developing web and mobile applications, among other things, there are really important differences between them.

Java was created in 1991 by James Gosling, and since then has become one of the most used programming languages in the world. After its creation, it took a group of Sun Microsystems engineers 4 years to develop Java. Other than the web and mobile applications, Java is also used in embedded systems, desktop applications, and scientific applications among other things. 3 billion devices around the world including computers, printers, smartphones, kindles, ATMs, home security systems, are using Java programming language. 

JavaScript, which was created in 1995 as a scripting language for the web, was known as Mocha back then. It took Brendan Eich 10 days to develop it. After a while, its name was changed to LiveScript, and then to JavaScript, mostly as a marketing tactic to associate it with an already popular programming language, Java. Other than the name, Java and JavaScript are not related to each other in any way.

**The Main Differences between Java and JavaScript**


**The Programming Paradigm:**

The programming paradigm is the way a programming language approaches a problem to solve it. Java is an Object-Oriented Programming (OOP) language, which means that Java is based on the concept of “Objects”, similar to the real-world objects. An object can have a name, properties, features, or functions associated with it. It can also have its own data, and it can decide how to share that data with other objects. OOP has allowed java to become the industry standard, especially in the enterprise domain. Although Java also supports functional programming, it is mostly used as an OOP language.

JavaScript, which was initially created as a scripting language, is now also used as a programming language together with third-party platforms and frameworks like NodeJs and ReactJs. JavaScript can also be used as a “functional programming language”, which is different from OOP. The functional programming style revolves around the use of functions to achieve a task and functions are considered as “first-class citizens”. So JavaScript is considered as a multi-paradigm language, as it can be used as OOP, Procedural or functional programming language.  This has helped Javascript to adapt to a diverse range of industries, and today javascript has become one of the most popular programming languages in the world. From front end to server-side programming, from scientific applications to artificial intelligence, javascript has quickly risen to the top as the preferred language.

**Syntax and Features:** 

Syntax determines how a particular programming language is written by programmers. Java and Javascript, both have significant differences when it comes to the syntax and features:

**Type Checking:** 

A language can be statically typed or dynamically typed. Type checking refers to the process of verifying and enforcing the “type” of a variable. Javascript is a dynamically typed language, meaning that the type of a variable is not known until the program is compiled. Also, a variable is not bound to a type before the compilation. Variables are declared with “var” or “let” keywords, and the compiler then automatically determines the type of the variable, based on the data it contains, like an integer, or a character.

Java on the other hand is statically typed, which means that each variable has to be associated with a “type” when it is declared. It makes the job of the compiler a lot easier and also prevents runtime errors, as the compiler can detect the mistakes before the program is executed.


**Inheritance:**

Inheritance is the mechanism by which one entity can acquire the properties of another entity. In Java, a ‘class’ can inherit properties from another ‘class’. It can also inherit from multiple classes, which is called multiple inheritances.

Javascript does not support multiple inheritances, as it is based on the concept of prototypes. Each object in javascript has a prototype, and it can point to another object to which it is inheriting from. It creates a prototype chain between the two objects. But each prototype can only connect to one object, and hence, javascript can not support multiple inheritances.


**Function Overloading:** 
It refers to the ability of a programming language to have two or more functions with the same name, which perform different tasks. In order to achieve this, the functions with the same name must have different signatures. Java supports function overloading, whereas javascript does not. Function overloading can bring flexibility in the hands of a programmer, but can also make it hard to debug.


**Multithreading:**

Multithreading in the context of a programming language is its ability to execute more than one part of a program concurrently in order to reduce the execution time of the program by utilizing CPU power.

Java supports multithreading by spawning and executing multiple ‘threads’. 

Javascript does not support multithreading because it is executed inside a browser, and the interpreter inside the browser is single-threaded. Although multithreading can make the program run faster, it can also induce complexity in the program and make it harder to debug and test. It also increases the chances of a deadlock, which makes it kind of a double-edged sword.

**Closures:**

The closure is a programming construct where a function can be passed as an argument to another function. Javascript supports closures, whereas Java doesn’t.

**Compilation and execution:** 

This is one more area where the two languages differ significantly. Java programs are compiled and interpreted to bytecode before they are executed by the Java Virtual Machine (JVM). This makes Java platform-independent, as different platforms can execute the same bytecode with the help of JVM. 

Javascript is mainly interpreted in the browser, as it is a scripting language. Javascript is written according to the browser specifications, as programs written for one browser might not execute properly in another.

The above differences clearly illustrate the fact that Java and Javascript are two completely different languages, and have very little in common.

<table>
  <tr>
   <td>Basis of Comparison
   </td>
   <td>Java
   </td>
   <td>JavaScript
   </td>
  </tr>
  <tr>
   <td>OOPS
   </td>
   <td>Java is an object-oriented programming language which uses objects to perform any actions based on relations between objects.
   </td>
   <td>JavaScript is an object-oriented scripting language which uses objects similar to Java.
   </td>
  </tr>
  <tr>
   <td>Running Platform
   </td>
   <td>Java applications and programs run in JVM (Java virtual machine) which required installing JDK and JRE on a system.
   </td>
   <td>JavaScript applications run on a web browser and no need of any initial setup.
   </td>
  </tr>
  <tr>
   <td>Mobile applications
   </td>
   <td>Old mobile applications are mostly written in Java and smartphone platforms like Symbian and Android also support Java
   </td>
   <td>Using JavaScript we can develop mobile applications but there are few limitations as we need to use third-party tools like phone gap to convert it to native code which mobile OS/platform can execute.
   </td>
  </tr>
  <tr>
   <td>Learning Curve
   </td>
   <td>Java has extensive documentation, online sources, online forums, communities from which one can learn easily. If we want to build applications and programming we can learn Java.
   </td>
   <td>JavaScript also has extensive documentation, online sources, online forums and communities by which one can learn easily as we can see its execution in the browser immediately. If we want to make websites or web applications we can learn JavaScript.
   </td>
  </tr>
  <tr>
   <td>Compilation
   </td>
   <td>Java programs are compiled and interpreted as it is a programming language.
   </td>
   <td>Whereas JavaScript is interpreted as it is scripting language which is a plain text code.
   </td>
  </tr>
  <tr>
   <td>Support
   </td>
   <td>Java is supported by most of the operating systems as almost every operating system supports.
   </td>
   <td>JavaScript is supported by most of the web browsers that come with different operating systems and developers can directly create scripts using JavaScript as it will be straightforward.
   </td>
  </tr>
  <tr>
   <td>Syntax
   </td>
   <td>Java language syntax is similar to C/C++ programming language</a>. Java program will be in classes and objects.
   </td>
   <td>JavaScript language syntax is similar to C language but naming conventions are similar to Java programming language.
   </td>
  </tr>
  <tr>
   <td>Scope
   </td>
   <td>Java is available almost everywhere and it is an independent programming language which can run on different operating systems. Java uses block-based scoping where variable goes out of scope once control comes out of a block.
   </td>
   <td>JavaScript is mostly used on web browsers and rely on HTML and CSS due to which it is not available globally. JavaScript uses function-based scoping as the variable can be accessed in the function.
   </td>
  </tr>
<tr>
   <td>IDE
   </td>
   <td>It has <a href="https://hackr.io/blog/best-java-ides"]various Java IDEs</a> like, Eclpise, netbean, jetbrains and ETC
   </td>
   <td>JavaScript has also many IDEs i.e. Atom, AWS Cloud9, Brackets, Codeanywhere
   </td>
  </tr>
</table>