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Interview Questions - JavaScript

JavaScript is among the most powerful and flexible programming languages of the web. Prepare for JavaScript / Web Developer interviews and get hired.
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This video course by Uplatz focuses on commonly asked interview questions on JavaScript.


JavaScript is a lightweight, interpreted programming language. It is designed for creating network-centric applications. It is complimentary to and integrated with Java. JavaScript is very easy to implement because it is integrated with HTML. It is open and cross-platform. JavaScript is among the most powerful and flexible programming languages of the web. It powers the dynamic behavior on most websites. JavaScript is a must for students and working professionals to become a great Software Engineer specially when they are working in web development domain.


Are you seeking for a career as a software engineer or a JavaScript developer? This is the course you've been looking for! This course is particularly designed to help you prepare for any upcoming JavaScript coding interviews. Interviews for programmers are notorious for being stressful and demanding, but they don't have to be! Preparation is the key to a successful coding interview. This course will help you prepare for coding interviews by covering the three most crucial topics: data structures, algorithms, and practise interview questions.


The data structures, algorithms, and interview questions we'll go through in this course are all based on real-world interviews with actual firms. The goal of this course is not for you to memorise the exercises, but rather for you to obtain a thorough grasp of how the javascript code works below the hood. You will be able to succeed in any interview questions that you may be asked in real life if you truly grasp how the code works. The goal of this course is for you to master the critical skills, tactics, and ideas that will help you thrive in any real-world interview questions. When you finish this course, you will have a solid grasp of data structures, algorithms, and interview questions, but more significantly, you will have mastered the ideas, skills, and approaches that will enable you to thrive in any other interview questions. You'll have a lot more confidence heading into any JavaScript interviews you have.


These Java Script Interview Questions & Answers by Uplatz have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of Java Script.  Normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer. This most commonly asked interview questions and answers bank will help you crack job interviews on JavaScript roles such as JavaScript Developer, Web Programmer, Full Stack Web Developer, and so on. The questions covers prominent JavaScript topics such as introduction to JavaScript, conditionals, functions, scope, arrays, loops, iterators, objects, classes, browser compatibility and transpilation, modules, promises, async-await, requests, and more.

Course/Topic - Interview Questions - JavaScript - all lectures

  • In this JavaScript Interview Questions tutorial, you will get to know about the different questions being asked by the interviewers in an interview and their answers regarding JavaScript like What is JavaScript, the difference between JavaScript and JScript, how to add JavaScript onto a web page among many others which will help you in clearing any JavaScript interview and get a high paid job in an organization.

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Course Objectives Back to Top

Be extremely well prepared for any javascript programming interviews you may have 

Perform admirably on a broad range of javascript interview questions 

Learn and grasp how algorithms operate and how to code them out

How to write out crucial data structures in JavaScript 

Create your own, bespoke algorithms that can do any task you want

If you want to become a JavaScript professional and are preparing for a job interview, then this JavaScript interview questions and answers guide will help you land your dream job.

It will also help you understand the fundamental concepts of JavaScript.

It will help you get your dream come true if you dreamt of your job as a JavaScript Programming developer or JavaScript programming sector.


Course Syllabus Back to Top
Certification Back to Top

The  JavaScript Certification ensures you know planning, production and measurement techniques needed to stand out from the competition. 

According to the Java platform official website, the main difference between Java and JavaScript is that Java is an OOP programming language while JavaScript is an OOP programming script. JavaScript code is written completely in text and need only be interpreted. Java, on the other hand, must be compiled.

JavaScript is a text-based programming language used both on the client-side and server-side that allows you to make web pages interactive. Where HTML and CSS are languages that give structure and style to web pages, JavaScript gives web pages interactive elements that engage a user.

If you definitely do not like front-end work, it is possible to find a job with only JavaScript, but it's an unusual path. You will likely have an easier time finding a role if you learn a different server-side language like Python or Go as well as JavaScript.

Uplatz online training guarantees the participants to successfully go through the JavaScript Certification provided by Uplatz. Uplatz provides appropriate teaching and expertise training to equip the participants for implementing the learnt concepts in an organization.

Course Completion Certificate will be awarded by Uplatz upon successful completion of the JavaScript online course.

Career & Jobs Back to Top

The JavaScript draws an average salary of $140,000 per year depending on their knowledge and hands-on experience.

A JavaScript developer also works together with other front end web developers who specialize in the markup and styling of applications. JavaScript developer is responsible for the programming and development of applications. He is also responsible for: Developing and enhancing the main front end platform website.

With a strong JavaScript foundation, you can transition into a lot of other professions like becoming a front-end and back-end web developer, mobile app developer, and machine learning engineer. Undoubtedly, becoming a JavaScript developer will make you highly employable and offer you great earning potential.

Yes you can get a job even if you only know JavaScript. However it needs to be the latest version and you should know how to use it efficiently. Which means most you must be knowing about promises, async await, ajax calls, etc.

Note that salaries are generally higher at large companies rather than small ones. Your salary will also differ based on the market you work in.

JavaScript Developer.

Software Developer.

JavaScript Lead.

Sr. JavaScript Developer.


Interview Questions Back to Top

1) What is JavaScript?

JavaScript is a scripting language. It is different from Java language. It is object-based, lightweight, cross-platform translated language. 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. More details.

2) List some features of JavaScript.

Some of the features of JavaScript are:

o   Lightweight

o   Interpreted programming language

o   Good for the applications which are network-centric

o   Complementary to Java

o   Complementary to HTML

o   Open source

3) Who developed JavaScript, and what was the first name of JavaScript?

JavaScript was developed by Brendan Eich, who was a Netscape programmer. Brendan Eich developed this new scripting language in just ten days in the year September 1995. At the time of its launch, JavaScript was initially called Mocha. After that, it was called Live Script and later known as JavaScript.

4) List some of the advantages of JavaScript.

Some of the advantages of JavaScript are:

o   Server interaction is less

o   Feedback to the visitors is immediate

o   Interactivity is high

o   Interfaces are richer

5) List some of the disadvantages of JavaScript.

Some of the disadvantages of JavaScript are:

o   No support for multithreading

o   No support for multiprocessing

o   Reading and writing of files is not allowed

o   No support for networking applications.

6) Define a named function in JavaScript.

The function which has named at the time of definition is called a named function. For example

1.     function msg()  

2.     {  

3.       document.writeln("Named Function");  

4.     }  

5.     msg();  

7) Name the types of functions

The types of function are:

o   Named - These type of functions contains name at the time of definition. For Example:

1.     function display()  

2.     {  

3.       document.writeln("Named Function");  

4.     }  

5.     display();  

o   Anonymous - These type of functions doesn't contain any name. They are declared dynamically at runtime.

1.     var display=function()  

2.     {  

3.       document.writeln("Anonymous Function");  

4.     }  

5.     display();  

8) Define anonymous function

It is a function that has no name. These functions are declared dynamically at runtime using the function operator instead of the function declaration. The function operator is more flexible than a function declaration. It can be easily used in the place of an expression. For example:

1.     var display=function()  

2.     {  

3.       alert("Anonymous Function is invoked");  

4.     }  

5.     display();  

9) Can an anonymous function be assigned to a variable?

Yes, you can assign an anonymous function to a variable.

10) In JavaScript what is an argument object?

The variables of JavaScript represent the arguments that are passed to a function.

Course Quiz Back to Top
Start Quiz
Q1. What are the payment options?
A1. We have multiple payment options: 1) Book your course on our webiste by clicking on Buy this course button on top right of this course page 2) Pay via Invoice using any credit or debit card 3) Pay to our UK or India bank account 4) If your HR or employer is making the payment, then we can send them an invoice to pay.

Q2. Will I get certificate?
A2. Yes, you will receive course completion certificate from Uplatz confirming that you have completed this course with Uplatz. Once you complete your learning please submit this for to request for your certificate https://training.uplatz.com/certificate-request.php

Q3. How long is the course access?
A3. All our video courses comes with lifetime access. Once you purchase a video course with Uplatz you have lifetime access to the course i.e. forever. You can access your course any time via our website and/or mobile app and learn at your own convenience.

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A4. Video courses cannot be downloaded, but you have lifetime access to any video course you purchase on our website. You will be able to play the videos on our our website and mobile app.

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A5. We do not take exam as part of the our training programs whether it is video course or live online class. These courses are professional courses and are offered to upskill and move on in the career ladder. However if there is an associated exam to the subject you are learning with us then you need to contact the relevant examination authority for booking your exam.

Q6. Can I get study material with the course?
A6. The study material might or might not be available for this course. Please note that though we strive to provide you the best materials but we cannot guarantee the exact study material that is mentioned anywhere within the lecture videos. Please submit study material request using the form https://training.uplatz.com/study-material-request.php

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A7. Please refer to our Refund policy mentioned on our website, here is the link to Uplatz refund policy https://training.uplatz.com/refund-and-cancellation-policy.php

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A8. We run promotions and discounts from time to time, we suggest you to register on our website so you can receive our emails related to promotions and offers.

Q9. What are overview courses?
A9. Overview courses are 1-2 hours short to help you decide if you want to go for the full course on that particular subject. Uplatz overview courses are either free or minimally charged such as GBP 1 / USD 2 / EUR 2 / INR 100

Q10. What are individual courses?
A10. Individual courses are simply our video courses available on Uplatz website and app across more than 300 technologies. Each course varies in duration from 5 hours uptop 150 hours. Check all our courses here https://training.uplatz.com/online-it-courses.php?search=individual

Q11. What are bundle courses?
A11. Bundle courses offered by Uplatz are combo of 2 or more video courses. We have Bundle up the similar technologies together in Bundles so offer you better value in pricing and give you an enhaced learning experience. Check all Bundle courses here https://training.uplatz.com/online-it-courses.php?search=bundle

Q12. What are Career Path programs?
A12. Career Path programs are our comprehensive learning package of video course. These are combined in a way by keeping in mind the career you would like to aim after doing career path program. Career path programs ranges from 100 hours to 600 hours and covers wide variety of courses for you to become an expert on those technologies. Check all Career Path Programs here https://training.uplatz.com/online-it-courses.php?career_path_courses=done

Q13. What are Learning Path programs?
A13. Learning Path programs are dedicated courses designed by SAP professionals to start and enhance their career in an SAP domain. It covers from basic to advance level of all courses across each business function. These programs are available across SAP finance, SAP Logistics, SAP HR, SAP succcessfactors, SAP Technical, SAP Sales, SAP S/4HANA and many more Check all Learning path here https://training.uplatz.com/online-it-courses.php?learning_path_courses=done

Q14. What are Premium Career tracks?
A14. Premium Career tracks are programs consisting of video courses that lead to skills required by C-suite executives such as CEO, CTO, CFO, and so on. These programs will help you gain knowledge and acumen to become a senior management executive.

Q15. How unlimited subscription works?
A15. Uplatz offers 2 types of unlimited subscription, Monthly and Yearly. Our monthly subscription give you unlimited access to our more than 300 video courses with 6000 hours of learning content. The plan renews each month. Minimum committment is for 1 year, you can cancel anytime after 1 year of enrolment. Our yearly subscription gives you unlimited access to our more than 300 video courses with 6000 hours of learning content. The plan renews every year. Minimum committment is for 1 year, you can cancel the plan anytime after 1 year. Check our monthly and yearly subscription here https://training.uplatz.com/online-it-courses.php?search=subscription

Q16. Do you provide software access with video course?
A16. Software access can be purchased seperately at an additional cost. The cost varies from course to course but is generally in between GBP 20 to GBP 40 per month.

Q17. Does your course guarantee a job?
A17. Our course is designed to provide you with a solid foundation in the subject and equip you with valuable skills. While the course is a significant step toward your career goals, its important to note that the job market can vary, and some positions might require additional certifications or experience. Remember that the job landscape is constantly evolving. We encourage you to continue learning and stay updated on industry trends even after completing the course. Many successful professionals combine formal education with ongoing self-improvement to excel in their careers. We are here to support you in your journey!

Q18. Do you provide placement services?
A18. While our course is designed to provide you with a comprehensive understanding of the subject, we currently do not offer placement services as part of the course package. Our main focus is on delivering high-quality education and equipping you with essential skills in this field. However, we understand that finding job opportunities is a crucial aspect of your career journey. We recommend exploring various avenues to enhance your job search:
a) Career Counseling: Seek guidance from career counselors who can provide personalized advice and help you tailor your job search strategy.
b) Networking: Attend industry events, workshops, and conferences to build connections with professionals in your field. Networking can often lead to job referrals and valuable insights.
c) Online Professional Network: Leverage platforms like LinkedIn, a reputable online professional network, to explore job opportunities that resonate with your skills and interests.
d) Online Job Platforms: Investigate prominent online job platforms in your region and submit applications for suitable positions considering both your prior experience and the newly acquired knowledge. e.g in UK the major job platforms are Reed, Indeed, CV library, Total Jobs, Linkedin.
While we may not offer placement services, we are here to support you in other ways. If you have any questions about the industry, job search strategies, or interview preparation, please dont hesitate to reach out. Remember that taking an active role in your job search process can lead to valuable experiences and opportunities.

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Q20. How do I access my course after payment?
A20. Once you have made the payment on our website, you can access your course by clicking on the "My Courses" option in the main menu or by navigating to your profile, then the student dashboard, and finally selecting "Video Courses".

Q21. Can I get help from a tutor if I have doubts while learning from a video course?
A21. Tutor support is not available for our video course. If you believe you require assistance from a tutor, we recommend considering our live class option. Please contact our team for the most up-to-date availability. The pricing for live classes typically begins at USD 999 and may vary.