JavaScript is a popular language in web development. You can use it to create front ends as well as back ends of a Website or App. Developers use it to create network-centric applications. It is an interpreted language. Every student who wants to learn web development must learn JavaScript. 

You don’t need to install any environment if you want to work on JavaScript. Almost all browsers have pre-installed JavaScript on them. You can also create desktop as well as mobile apps using JavaScript. It has many popular frameworks and libraries that you can use directly for development. Some of the popular frameworks are ReactJS, NodeJS, jQuery, Vue.js, and Angular.


Features of Online Javascript Compiler

  • It can be accessed through any web browser
  • Easy to use interface and supports various libraries.
  • The syntax highlighting feature colours the elements of the code to increase readability.
  • Compiler’s Autocompletion feature accelerates coding by predicting already defined variables/functions and completing code.


Syntax help

In Javascript, you can declare variables using var, let, and const keywords. 

var: It is the old way to declare a variable. The scope is global 

let: It is a new way of declaring a variable. The scope is global or block.

const: It helps you to declare constants. The scope is global or block.


1. If statement:

The“if” statement checks the condition specified in the “if” bracket. If the condition is true, only then it will run the code in the block.


if(condition_to_check) {
// If the condition is true, this block will execute.

2. If-Else Statement:

The if statement checks the condition. If it is true, the code in the “if” block will execute. If it is false, the code in the “else” block will execute.  


if(condition_to_check) {
// If the condition is true, this block will execute.
} else {
// If the condition is false, this block will execute.

3. Switch Statement:

The “switch” statement has multiple blocks of code. The code will run based on the case or condition specified.


switch(condition_or_expression) {
case A:
// This block will run if the case value matches with the expression.
case B:
     // This block will run if the case value matches with the expression.
     // This block will run if none case value matches with the expression.

4. For Loop:

The “for” loop helps to execute one block of code multiple times. It has three conditions.


for (exp_1; exp_2; exp_3) {
// The block of code that you want to execute more than once.
“exp_1” will execute only once in the beginning.
“exp_2” is the condition for the execution of the block of code.
“exp_3” will execute each time after the execution of the block of code.


5. While Loop:

The “while” loop will run only till the condition specified in the brackets is true.


while (condition_to_check) {
// The block of code that you want to execute more than once.


6. Do-While Loop:

The “do-while” is a variation of the “while” loop. The only difference is that the code will run one time even before checking the condition. After the first time, the running of the code will be dependent on the condition.


do {
// The block of code that you want to execute more than once.
while (condition_to_check);


Classes in Javascript

In Javascript, a class is a template used to create an object. Classes help you to work with the concepts of Object Oriented Programming in JavaScript. To create a class, you need to use the “class” keyword. Keep in mind that you always need to create a constructor() method. It helps to initialize the properties of the object.


// The creation of a class.
class NameOfTheClass {
constructor(testname) {
this.testname = testname;
// We will create an object of the class.
const object1 = new NameOfTheClass('Pranav');
const object2 = new NameOfTheClass('Swati');
// We will print both objects
console.log(object1.testname); // Pranav
console.log(object2.testname); // Swati




Arrays in Javascript 

Arrays help you to work with a list of items in a single variable. A single array can have more than one value. You can specify the index if you want to access the values in the arrays.


<!DOCTYPE html>
    <h2>Example of Arrays in JavaScript</h2>
      var vehicle=["Car","Bike","Scooter"];  
      for(j=0; j<vehicle.length; j++) {  
        document.write(vehicle[j] + "<br/>");  


Example of Arrays in JavaScript





Arrow functions in Javascript

The Arrow function helps you to shorten the syntax of a function. It was introduced in ES6.


let functionName = (argument1, argument2, ...argumentN) => {
    // the statement that will run.

The function name is “functionName”.

The function arguments are argument1, argument2, …argumentN.

The statement will be put inside the curly braces. 


let add = (x, y) => {
// To store and return the result.
let answer = x + y;
return answer;
let result = add(2,6);
console.log("The sum of the inputs are: ");


Working on the Online Javascript Compiler

Compilers are specialised software tools that convert the source code of one programming language into machine code, bytecode, or another programming language. Typically, the source code is created using a high-level, understandable language like Javascript. An integrated development environment (IDE) or a code editor is used by the programmer to write the source code, which is then saved to one or more text files. The files are read, the code is examined, and it is then translated into a format appropriate for the target platform by a compiler that supports the source programming language.

Using an online compiler to compile Javascript code is very easy, You just need to type the code in the provided editor and provide any custom input if required. Then just press run and the result will be immediately displayed.


How to write and run the javascript programs online?

JavaScript is an interpreted language. Before execution of any program, you must compile it first. Compilers are software tools that take source code and convert it into an executable machine-readable byte. You can use the online versions of the compilers as well. The online compiler of JavaScript on CodingNinjas allows you to compile JavaScript code completely free. You don’t need to download any software or compiler. You just need a browser to open the website. You can just write the code and compile it. In case of errors, you can also debug it.


Benefits of using Online Javascript Compiler

Using an online Javascript Compiler as opposed to using a local compiler has many advantages. Some of them are as follows:

  • Faster Execution: Online Compilers are often running on powerful servers which have the capacity of running complex codes in less time. Hence as compared to running code locally on a weak machine, running code online is faster.
  • No hassle: To run code locally, users will need to install software and online compilers. But to run code online, users will just need to open the link and click one button.
  • Fairly Simple: Using local compilers often provide users with many different options which often overwhelms the user. In contrast, online compilers have a simple interface.
  • No burden: If running code locally, the CPU of the machine is intensively used to run the code which may cause the machine to lag or overheat.
  • More productive: Users can compile the code from anywhere anytime.



  • Compiler: A compiler is an essential tool that can be used locally or online for compiling a code, that is, converting the code to a machine based language for output.
  • Interpreter: An Interpreter is a tool that works similarly to a compiler, converting high level code into machine based language, but it converts the code line by line rather than in a single pass.
  • Online IDE: Online IDE, or Integrated Development Environment, is a software based tool that is used as a single platform for all kinds of computer programming. It consists of an integrated compiler or interpreter, extensions, dependency files, and a debugger. Example: Eclipse
  • Code Editor: A Code Editor is another essential part of computer programming. It is a place where all source codes can be created and modified. It can be a stand alone application or part of an IDE. Example: Vim and Sublime
  • Coding Ground: Coding Ground is a tool that provides easy accessibility to developers for using more than one programming language, technology, and framework. It allows developers to use various tools on a single platform.