Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and Answers Freshers, Knockout JS Interview Questions and Answers, Knockout JS Interview Questions

Before getting on to the Knockout JS interview questions, the student must know that the Knockout JS is a continuously varying field which needs the students as well as professionals to upgrade their skills with the new features and knowledge, to get fit for the jobs associated with Knockout JS. This post related to Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and Answers Freshers, Knockout JS Interview Questions and Answers, Knockout JS Interview Questions will help you let out find all the solutions that are frequently asked in you upcoming Knockout JS interview.

Over thousands of vacancies available for the Knockout JS developers, experts must be acquaintance with all the component of Knockout JS technologies. This is necessary for the students in order to have in-depth knowledge of the subject so that they can have best employment opportunities in the future. Knowing every little detail about Knockout JS is the best approach to solve the problems linked with problem.

APTRON has spent hours and hours in researching about the Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and Answers Freshers, Knockout JS Interview Questions and Answers, Knockout JS Interview Questions that you might encounter in your upcoming interview.  All these questions will alone help you to crack the interview and make you the best among all your competitors.

First of all, let us tell you about how the Knockout JS technology is evolving in today’s world and how demanding it is in the upcoming years. In fact, according to one study, most of the companies and businesses have moved to the Knockout JS. Now, you cannot predict how huge the future is going to be for the people experienced in the related technologies.

Hence, if you are looking for boosting up your profile and securing your future, Knockout JS will help you in reaching the zenith of your career. Apart from this, you would also have a lot of opportunities as a fresher.

These questions alone are omnipotent. Read and re-read the questions and their solutions to get accustomed to what you will be asked in the interview. These Knockout JS interview questions and answers will also help you on your way to mastering the skills and will take you to the giant world where worldwide and local businesses, huge or medium, are picking up the best and quality Knockout JS professionals.

This ultimate list of best Knockout JS interview questions will ride you through the quick knowledge of the subject and topics like Live Debugging, Inspecting Bindings, Custom Binding Handlers, Computed Observables. This Knockout JS interview questions and answers can be your next gateway to your next job as a Knockout JS expert.

These are very Basic Knockout JS Interview Questions and Answers for freshers and experienced both.

Q1: What is Knockout JS?
A1: Knockout JS is a JavaScript library based on MVVM (Model View ViewModel) pattern that helps you to create rich, responsive display and editor user interfaces with a clean underlying data model.

Knockout JS is small light weighted JavaScript library that is mostly used for designing an SPA (Single Page Application).

Q2: Types of data binding supported by Knockout JS?
A2: Knockout js supported two types of binding

  • One-way binding
  • Two-way binding

Q3: What is an observable in KnockoutJS?
A3: Observables: In KnockoutJS observables are special type of JavaScript objects that can notify subscribers about changes, and can automatically detect dependencies. Observables helps KnockoutJS to update your UI automatically when the view model changes.

Creating an Observable in KnockoutJS

var myViewModel = {
personName: ko.observable(‘Bob’),
personAge: ko.observable(123)

Q4: What are Components in Knockout JS?
A4: Components are a powerful, clean way of organizing your UI code into self-contained, reusable chunks.They:

  • ..can represent individual controls/widgets, or entire sections of your application
  • ..contain their own view, and usually (but optionally) their own viewmodel
  • ..can either be preloaded, or loaded asynchronously (on demand) via AMD or other module systems
  • ..can receive parameters, and optionally write back changes to them or invoke callbacks
  • ..can be composed together (nested) or inherited from other components
  • ..can easily be packaged for reuse across projects
  • ..let you define your own conventions/logic for configuration and loading

Q5: Why is KnockoutJS useful ?
A5: Knockout can dramatically reduce the amount of code needed to synchronize a data model and user interface controls. It is fast, cross browser compatible, and not reliant on any other libraries. It is lightweight (< 20kb after compression) and can be easily integrated with most web applications without any major architectural update.

Q6: What is a computed observable ?
A6: This is a special type of function that is dependant on one or more observables to work. For example, when the one or more observable value the computed is linked to changes, the computed observable gets called. The classic example is a computed called ‘Full Name’ which observes and combines ‘first name’ and ‘last name’ to make ‘Full name’.

Q7: How do you prepare a Knockout object for data transfer ?
A7: Data can be serialised to JSON using ko.toJSON(viewModel), and to a simple JavaScript object using ko.toJS(viewModel).

Q8: How can you control flow with bindings ?
A8: When you have an array of items in a Knockout viewModel, you can tell your mark-up to iterate through them using the data-bind ‘for-each’ for example.

Q9: How do you delete an item from a Knockout array ?
A9: Use the remove or removeAll methods, passing in the item you want to match for deletion.

Q10: Name two context properties in Knockout and explain their use
A10: When working with arrays, the $index property returns the index of the current context item in the array. When working with nested objects, the $parent property allows us to examine the parent of an object, for example a customer may have many orders, an order may have many line items. The order is the parent of the line item, the customer is the parent of the order.

Q11: What Is observable Arrays in Knockout JS?
A11: The Observable array is KnockoutJs properties that contain the item collection in the view model and this property is bind with UI (View) in two way binding.

Q12: What Is dependency tracking in KnockoutJs?
A12: In the dependency tracking, KnockoutJs automatically update the UI (DOM) when your data model is change.

Q13: What Is the KO and why we use, explain in details?
A13: The KO is a heart and soul of KnockoutJs that provides interdependent way to link the ViewModel to Model and ViewModel to UI (user interface).

The KO does not depend on the jQuery library, but we can use jQuery at the same time. Using KO you can handle client and server side application in simply manner.

Q14: Define $index property?
A14: $index property returns the index of the current context item in the array.

Q15: Define $parent property?
A15: $parent property allows us to examine the parent of an object.

Q16: What are the difference between KnockoutJs and MVC?

KnockoutJs MVC
KnockoutJs is a MVVM pattern MVC is a design pattern
It work like connected mode It work like disconnected mode
It supported two types of binding

One-way binding , two-waybinding

MVC supported only one-way binding.
UI part automatically update when your data model update In MVC, not update UI automatically when your data model update. Need event to call data model and update it.
Model part is not directly bind with the view page. Models directly bind with the view-model and view-model directly with the view page.  Model parts directly bind with the view page.

Q17: How KO intended to compete with jQuery or work with it?
A17: jQuery is an outstanding replacement for the clunky, inconsistent DOM API we had to put up with in the past. jQuery is an excellent low-level way to manipulate elements and event handlers in a web page. KO solves a different problem.

As soon as your UI gets nontrivial and has a few overlapping behaviors, things can get tricky and expensive to maintain if you only use jQuery. Consider an example: you’re displaying a list of items, stating the number of items in that list, and want to enable an ‘Add’ button only when there are fewer than 5 items. jQuery doesn’t have a concept of an underlying data model, so to get the number of items you have to infer it from the number of TRs in a table or the number of DIVs with a certain CSS class. Maybe the number of items is displayed in some SPAN, and you have to remember to update that SPAN’s text when the user adds an item. You also must remember to disable the ‘Add’ button when the number of TRs is 5. Later, you’re asked also to implement a ‘Delete’ button and you have to figure out which DOM elements to change whenever it’s clicked.

Q18: Describe ViewModel in Knockout Js?
A18: A viewModel in Knockout js is a basic class that is created as JavaScript Function.It is declared as a variable that have member variables and methods.

var myViewModel = {
personName: ‘Bob’,
personAge: function(age){
return age+”years old”;

Q19: What is the features of Knockout JS?
A19: Key Features of Knockout JS

  • Dependency Tracking
  • Declarative Binding
  • Automatic UI Refresh
  • Template Binding
  • Written in Pure JavaScript
  • Compact Size less than 20 kb.
  • Support all modern browsers
  • Easy to implement

Q20: How would you flag an item deleted and why is this useful ?
A20: In cases where you want to manage an array of existing data for example browser-side, and inform the server of both additions, changes and deletions, you can flag an array item using the ‘destroy’ or ‘destroyAll’ method. This creates a dirty record that is flagged “_destroy” and can be easily identified server-side for handling in the data repository.

Knockout JS Conclusion Interview FAQs

We know the list of Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and Answers Freshers, Knockout JS Interview Questions and Answers, Knockout JS Interview Questions is overwhelming but the advantages of reading all the questions will maximize your potential and help you crack the interview. The surprising fact is that this Knockout JS interview questions and answers post covers all the basic of the Knockout JS technology and you have to check out the FAQs of different components of Knockout JS too.

However, you will be asked with the questions in the interview related to the above mentioned questions. Preparing and understanding all the concept of Knockout JS technology will help you strengthen the other little information around the topic.

After preparing these interview questions, we recommend you to go for a mock interview before facing the real one. You can take the help of your friend or a Knockout JS expert to find the loop holes in your skills and knowledge. Moreover, this will also allow you in practicing and improving the communication skill which plays a vital role in getting placed and grabbing high salaries.

Remember, in the interview, the company or the business or you can say the examiner often checks your basic knowledge of the subject. If your basics is covered and strengthened, you can have the job of your dream. The industry experts understand that if the foundation of the student is already made up, it is easy for the company to educate the employ towards advance skills. If there are no basics, there is no meaning of having learnt the subject.

Therefore, it’s never too late to edge all the basics of any technology. If you think that you’ve not acquired the enough skills, you can join our upcoming batch of Knockout JS Training in Noida. We are one of the best institute for Knockout JS in noida which provide advance learning in the field of Knockout JS Course. We’ve highly qualified professionals working with us and promise top quality education to the students.

We hope that you enjoyed reading Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and Answers Freshers, Knockout JS Interview Questions and Answers, Knockout JS Interview Questions and all the FAQs associated with the interview. Do not forget to revise all the Knockout JS interview questions and answers before going for the Knockout JS interview. In addition to this, if you’ve any doubt or query associated with Knockout JS, you can contact us anytime. We will be happy to help you out at our earliest convenience. At last, we wish you all the best for your upcoming interview on Knockout JS Technology.