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Knockout js Interview Questions

Top knockout js interview questions

Below are the list of Top knockout.js interview questions and their answers

  1. What is Knockout JS?
  2. List some features of Knockout JS?
  3. Types of data binding supported by Knockout JS?
  4. Describe ViewModel in Knockout Js?
  5. What is an observable in KnockoutJS?
  6. What are Components in Knockout JS?
  7. How to check an observable is null in knockout js
  8. How can you format currency in knockout.js

1. What is Knockout JS?

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).

2. What is the features of Knockout JS?

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

3. Types of data binding supported by Knockout JS?

Knockout js supported two types of binding

  • One-way binding
  • Two-way binding

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4. Describe ViewModel in Knockout Js?

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";

5. What is an observable in KnockoutJS?

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)

6. What are Components in Knockout JS?

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

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