Online Javascript Compiler

To start your javascript programming journey you first need to understand interpreters and compilers.

An interpreter is a program that reads and executes code line by line. In the case of JavaScript, the interpreter can be built into a web browser, allowing the browser to interpret and execute JavaScript code directly. When a user visits a website with JavaScript code, the interpreter in the browser reads and executes the code on the fly, providing dynamic and interactive content to the user.

On the other hand, a compiler is a program that takes the entire code and translates it into machine language, which can be directly executed by the computer. In the case of JavaScript, a compiler can be used to translate JavaScript code into a lower-level language that can be run more efficiently, resulting in faster execution times.

As we know, JavaScript can be both interpreted and compiled, depending on the implementation and context in which it is used.

Scaler Topics comes with an IDE that is very feasible enough to compile, test, and run Javascript programs online easily for free.

Working of the Javascript Compiler

Given below are some of the steps of our Compiler that users might find helpful:

The first step is your need to sign in to use this compiler's features. It is possible to run your code without signing in but you will not have a track to your previous codes here, so it's advisable to sign in to enjoy its cool features. Click on the button present at the top right corner and a window will appear.

  • Code Editor: Write code in the code editor (which has syntax highlighting for more code readability). For users who are logged into the Scaler Topics Platform, the total number of characters in their code can go up to five thousand characters. For non-Scaler Topics Users, their Python code can have up to five hundred characters.
  • RUN: In order to run a Python program, a user can write python code in the editor and then click on the ‘RUN’ button after selecting the appropriate compiler version.
  • SAVE: The Python code written in the editor can be saved by clicking on the ‘SAVE’ button on the top right corner of the webpage. The saved codes can be accessed using the ‘MY SNIPPETS ’ button on the webpage.
  • STDIN & STDOUT: In order to feed input to the Python Code, users can use the Standard Input (stdin) console of our compiler and the output of the code appears on the Standard Output (stdout) of the compiler.
  • SAVE: The programs saved can be made public - available for all - or private - accessible to only the code owner.
  • FORK: Public code snippets can also be forked or downloaded in the ‘NEW’ section using the ‘FORK’ button. After forking a code, one can reuse it as per requirement.
  • SHARE: Now that you have your code ready, you might need to share it with people. Our compiler also supports sharing of code in Read-Only Format. This can be done using the ‘SHARE’ button on the top right corner of the webpage.


let x = 10;
console.log(x + " is a number");


10 is a number

Learn Javascript - Practice Online

What is Javascript?

JavaScript is a very powerful language. It has the power to add interactivity to static websites(built using HTML and CSS), apply dynamic styles, add or delete HTML elements dynamically, and much more. So, whenever you try to submit an empty form and an error message pops up, you should know that it's JavaScript behind that!

JavaScript is the language of browsers. Whenever we write JavaScript, the browser will execute that code for us. If we want to write JavaScript away from browsers, we need Node.js, which is the run-time environment for JavaScript. It is used to write JavaScript for the back end.

Hence, JS can be used to add interactivity to the front end of the web apps and create servers to run the back end using Node.Js.

Why Learn Javascript?

If you want to explore the web and see how interactions work on websites and web applications, you must learn JavaScript.

You can use JavaScript to create super-fast websites and web applications. It provides a great experience to the users while interacting with your website.

JavaScript is built into almost all modern web browsers by default. No setup or software is required to run JavaScript. Chrome, Safari, Mozilla Firefox, or any other web browser you can think of; support JavaScript.

You can use JavaScript to create front-end and back-end for your website or web application. JavaScript in its raw form can be used to make a front-end for web applications. In addition, we can use frameworks and libraries, like React, Vue, Angular, etc., to primarily make the browser do lesser work and increase speed.

For the back end, we can use JavaScript server-side environments. A popular one is NodeJS. It is a run-time environment to run JavaScript on the server side. In addition, frameworks and libraries such as ExpressJs and NestJS can be used.

Features of JavaScript have been extended to mobile development and game development. Plus, front-end development is in huge demand in the market. Considering tons of opportunities and features this language has to offer, every student must learn this language, and Boyaa! You will have all the power to experiment with the web and build crazy web applications.

Features of JavaScript

Below listed are some of the main and popular features of JavaScript:

  • All modern web browsers have built-in environments for executing JavaScript.
  • It empowers developers to provide a good user experience to their users.
  • JavaScript is a weakly typed language. If you've ever written code in JAVA or C/C++, you know what creating types for each variable means. JavaScript frees you to write type-less code.
  • It is case-sensitive and interpreted language.
  • JavaScript is lightweight and super fast during execution.

Applications of JavaScript Programming

Today, most developers use JavaScript in some form or the other. JavaScript can be used to -

  • Create super fast and interactive front-end
  • Build backend for web-applications
  • For Game Development
  • To build mobile applications
  • For client-side validation
  • Manipulating DOM (Document Object Model) and BOM (Browser Object Model)

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Working on the Online Javascript Compiler

While compilers can convert source code into machine code or bytecode, JavaScript is not typically compiled in the traditional sense. This is because JavaScript code is designed to be run directly by a JavaScript engine, which interprets the code without first converting it to machine code. JavaScript is a high-level language that is intended to be run in a browser or similar runtime environment, rather than on a standalone computer. However, there are tools and techniques, such as Just-In-Time (JIT) compilers and Ahead-of-Time (AOT) compilers, that can optimize and accelerate the execution of JavaScript code. :::

Javascript Syntax

Following are some of the basic syntax that one should know to start their programming career in Javascript:

JavaScript Variables:

  • Variables are used to store data in memory
  • In JavaScript, variables can be declared using the keywords var, let, or const
  • Variables can hold various types of data, including numbers, strings, booleans, arrays, and objects


// Declare a variable using 'var' and assign it a value
var x = 5;

// Declare a variable using 'let' and assign it a value
let y = "Hello";

// Declare a constant variable using 'const' and assign it a value
const PI = 3.14;

// Re-assign the value of a variable
x = 10;

// Concatenate strings
let z = y + " World!";

// Use variables in an array
let myArray = [1, 2, 3, x, y];

// Create an object with variables as properties
let myObject = {
  name: "John",
  age: 30,
  occupation: "Developer"




Hello World!


  • for Loop: A for loop is used when you need to execute a block of code a specific number of times.
  • while Loop: A while loop is used when you need to execute a block of code while a certain condition is true.


for (let i = start; i <= end; i++) {

let i = start;
while (i <= end) {


for (let i = 1; i <= 2; i++) {



Conditional statements (if/else)

Javascript supports various decision-making statements like if, if..else, nested if, and switch case. We have discussed the basic ones:





let x = 5;

if (x > 10) {
  console.log("x is greater than 10");
} else {
  console.log("x is less than or equal to 10");


x is less than or equal to 10


  • Functions are one of the fundamental building blocks of JavaScript programming.
  • They allow you to group a set of statements together to perform a specific task.
  • Functions promote reusability and modularization of code, making the code easier to understand and maintain.


function function_name(parameters){
    code statement(s)


// Defining a function
function greet(name) {
  console.log("Hello, " + name + "!");

// Invoking the function


Hello, John!
Hello, Jane!

In this example, we define a function greet that takes a parameter name. The function simply logs a greeting message to the console, including the name parameter that was passed in. We then invoke the function twice, passing in different names each time, and the function logs the appropriate message for each.

How to compile and run the javascript programs online?

JavaScript is a programming language that is well-suited for beginners due to its simple syntax compared to other languages. Creating a JavaScript program using an online compiler is a straightforward process. To get started, simply navigate to the compiler's editor and begin typing your program. If you need assistance writing your program, I can provide an example for you. Just click on this link to navigate to the JavaScript compiler and input the following lines:

console.log("Welcome to Javascript Online Compiler by Scaler!!");


Welcome to Javascript Online Compiler by Scaler!!

Additional Resources


  • Online IDE: IDE is an acronym for Integrated Development Environment. Online Integrated Development Environments help programmers code in various languages and run, compile, and debug their codes online without having the need to download the respective programming compilers.
  • Compiler: In computing, a compiler is a computer program that is used to translate computer codes written in one programming language into another language.
  • Interpreter: Like Compilers, interpreters are also used to translate computer codes written in one programming language into another language. However, the difference between the two is that compiler compile the entire source code into machine code at once while interpreters convert the source code into machine code line by line.
  • Code Editor: A code editor is software used by programmers to code. Most code editors provide various features like syntax highlighting to make the code written on them more readable.
  • Coding Ground: Coding grounds are platforms that can be used to write and run codes written in various languages.