Top 10 Interview Questions for JavaScript

What is JavaScript?

JavaScript is a Scripting Language that allows you to build complex features on the web page. Like for example, displaying constant and timely images, updates, interactive maps, graphics, videos, and many more such features that are more than just static information. Moreover, JavaScript allows you to do things like-
(i) Store values inside variables
(ii) Running codes on web pages simultaneously when certain events are occurring on the web page.

Moreover, APIs (Application Programming Interfaces) provides extra functions to JavaScript so that they can function well.

Moving on, now when you have a brief idea of what is JavaScript and how it functions. We will further discuss the top 10 interview questions that you might face in an interview.

Well, grab a pen and a notebook and let’s get started –

1.       Do you know the difference between Java and JavaScript?
- Java is an OOP Programming Language that creates applications to run in a virtual machine or a browser and its codes needs to be complied whereas JavaScript is a scripting Language whose codes are run on browser only and its codes are in a form of a text.

2.       What Data Types are supported by JavaScript?
- JavaScript supports data types like:
(i) Undefined
(ii) Null
(iii) Boolean
(iv) Object
(v) Number
(vi) String
(vii) Symbol

3.       Is JavaScript case-sensitive?
- Yes, it is a case-sensitive language. It must be typed with the capitalization of letters.

4.       What is Call Back in JavaScript?
-  It is a plain JavaScript function that is executed after the previous function has completed its execution.

5.       What are Attributes and Property?
-  Attributes provides more details on elements like id, type, value etc. whereas Property is the value that is assigned to the property like type = text, Value = Name etc.

6.       Name some of the Frameworks used by JavaScript.
- Some of the frameworks used by JavaScript are -
(i) Angular
(ii) Vue
(iii) React

7.       What is NaN in JavaScript?
- NaN is the abbreviation for Not a Number in JavaScript. It indicates an error condition for a function that should return a valid number. When string is converted into a number then it shows error, there we can see NaN in JavaScript.

8.       What is Local Storage and Session Storage in JavaScript?
- Local Storage in JavaScript - The data is not sent back to the server for every HTTP request thus reducing the traffic between the client and the server. You need to clear the settings or programs to remove it.
Session Storage in JavaScript -  It is mostly like the Local Storage except for the fact that data stored in Session Storage has an expiration date. The data gets cleared when the page session ends.

9.       How many ways are there in which a JavaScript code can be involved in HTML file? Name them.
- There are three ways in which a JavaScript code can be involved in HTML file and they are -
(i) Inline – Assigned to variable at runtime.
(ii) Internal – You can have the script integrated on the page that you are working on.
(iii) External – You can have the script integrated on a separate file .

10.   Define Variables in a JavaScript.
- Three variables in a JavaScript are-
(i) Var – It is used to declare a variable and we can initialize the value of that variable.
(ii) Const- It doesn’t allow to modify the object on which they are called and can be called on any type of object.
(iii) Let – The variable can be reassigned and used only in block it’s defined in.

With this, we come to an end of this blog.

We hope that this will help you in preparation for your interview. Also, remember that good preparation can make you look confident.

All the Best!


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