Top Javascript Interview Questions with Answers

Some of the most frequently asked JavaScript interview questions with answers for beginners and professionals are given below.

Javascript is one of the most popular and widely accepted languages in programming language history. This makes it the perfect language to ask interview questions from, in various technical and programming interviews.

This is what this article is all about. In this post, we have corrugated the list of all the best and popular javascript interview questions with their answers, which are most commonly asked in programming interviews.

All the Javascript Interview questions will range from Basic Javascript to intermediate and finally, the interview questions will be about advanced javascript. So without wasting more time, let’s dive in.

Javascript Interview Questions

Basics Javascript Interview Questions

What is Javascript?

JavaScript is a very lightweight, interpreted programming language with object-oriented capabilities that allows you to build interactive webpages.

It is widely used for client-side validation. The JavaScript Translator (embedded in the browser) is responsible for translating the JavaScript code for the web browser. Javascript is developed by the Netscape company, the same company that built the Netscape browser.

Is there any similarity between Java and Javascript?

There is no similarity between Java and Javascript. Many people get confused by the name Java in Javascript but in reality, they are not related to each other at all.

Java is a complete programming language. In contrast, JavaScript is a coded program that can be introduced to HTML pages. These two languages are not at all inter-dependent and are designed for different intent.

Java is an object-oriented programming (OOPS) or structured programming languages like C++ or C whereas JavaScript is a client-side scripting language.

What are the features of Javascript?

Features of Javascript language are described below:

  1. Javascript is a very lightweight programming language.
  2. Open-source cross platform compatible programming language.
  3. It is designed for creating network-centric applications.

What are the different Data Types in Javascript?

In general, Javascript supports Data Types. These are the following ones:

  1. Undefined
  2. Null
  3. Boolean
  4. String
  5. Symbol
  6. Number
  7. Object

Is Javascript a Case-Sensitive Programming Language?

JavaScript is a case sensitive language. The language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

What are the advantages of using Javascript?

These are the advantage of using Javascript:

  1. With Javascript, more interactive web pages can be built.
  2. You can build really engaging interface using Javascript
  3. Server interaction is less as all the major validation can be done with the help of Javascript.
  4. Getting user feedback is more easy and instant.

How to create an object in Javascript?

JavaScript supports the Object concept very well. You can create an object using the following syntax:

var emp = {
name: "Codingshala",
age: 5

How to create an Array in Javascript?

Arrays can be created in Javascript using the following syntax:

var x = [];
var y = [1, 2, 3, 4, 5];

How to create a function in Javascript?

In Javascript, you can declare functions in two ways. The first one is the default one i.e by using the function operator. Here is the example of that

// ES5
function(x, y) {
  return x * y;

The second method is to use the arrow function. Here is the example of that also.

(x, y) => { return x * y };

How to declare variables in Javascript?

In Javascript, you can use var, let, and const keyword to declare a variable. A variable must have a unique name. You can assign a value to a variable using equal to (=) operator when you declare it or before using it.

What is the scope of variables in Javascript?

In Javascript, you have two scopes for your variables.

  1. Global Variables − A global variable has a global scope which means it is visible everywhere in your JavaScript code.
  2. Local Variables − A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.

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