Interview Questions and Answers
Know the top Knockout JS interview questions and answers for freshers and experienced candidates to prepare for job interviews.
Total 25 questions
Interview Questions and Answers
Interview Questions and Answers
Search a question to view the answer.
Search a question to view the answer.
Freshers / Beginner level questions & answers Ques 1
What is Knockout JS? Knockout JS is a JavaScript library that helps you to create rich, responsive display and editor user interfaces with a clean underlying data model.
Example:
var viewModel = { name: 'John', age: 25 }; ko.applyBindings(viewModel);
Ques 2
What is an observable in Knockout JS? An observable in Knockout JS is an object that can notify subscribers about changes, allowing the automatic updating of UI elements.
Example:
var observableValue = ko.observable('Initial value'); observableValue.subscribe(function(newValue) { console.log('New value:', newValue); });
Ques 3
What is the purpose of the 'data-bind' attribute in Knockout JS? The 'data-bind' attribute is used to associate HTML elements with Knockout JS data-bindings, enabling the establishment of a connection between the UI and the underlying view model.
Example:
; var viewModel = { message: 'Hello, Knockout!' }; ko.applyBindings(viewModel);
Ques 4
How can you handle click events in Knockout JS? You can use the 'click' binding to associate a function with a click event on an HTML element.
Example:
Click me; var viewModel = { handleClick: function() { alert('Button clicked!'); } };
Ques 5
What is the purpose of the 'text' binding in Knockout JS? The 'text' binding is used to set the text content of an HTML element based on the value of the associated observable or expression.
Example:
; var viewModel = { message: 'Hello, Knockout!' };
Ques 6
What is the purpose of the 'value' binding in Knockout JS? The 'value' binding is used to bind an input, select, or textarea element's value to an observable, allowing two-way data binding.
Example:
Ques 7
Explain the 'subscribe' method in Knockout JS. The 'subscribe' method is used to register a callback function that will be called whenever the associated observable's value changes.
Example:
var myObservable = ko.observable('Initial value'); myObservable.subscribe(function(newValue) { console.log('New value:', newValue); });
Ques 8
How does the 'checked' binding work in Knockout JS? The 'checked' binding is used to bind the checked state of a checkbox or radio input to an observable, enabling two-way data binding.
Example:
Ques 9
What is the purpose of the 'if' binding in Knockout JS? The 'if' binding is used to conditionally render or remove an HTML element based on the truthiness of the associated observable or expression.
Example:
; var viewModel = { shouldShowContent: ko.observable(true) };
Ques 10
What is the purpose of the 'options' binding in Knockout JS? The 'options' binding is used to generate a set of 'option' elements based on an array or object and bind the selected value to an observable.
Example:
; var viewModel = { countries: ['USA', 'Canada', 'UK'], selectedCountry: ko.observable('USA') };
Intermediate / 1 to 5 years experienced level questions & answers Ques 11
Explain two-way data binding in Knockout JS. Two-way data binding in Knockout JS ensures that when the UI changes, the underlying data model is automatically updated, and vice versa.
Example:
HTML:
Ques 12
How does the 'foreach' binding work in Knockout JS? The 'foreach' binding is used to iterate over an array and generate content for each item in the array within the specified HTML element.
Example:
HTML:
; JavaScript: var items = ko.observableArray(['Item 1', 'Item 2']); ko.applyBindings({ items: items });
Ques 13
Explain the 'visible' binding in Knockout JS. The 'visible' binding is used to control the visibility of an HTML element based on the truthiness of the associated observable or expression.
Example:
; var viewModel = { showElement: ko.observable(true) };
Ques 14
Explain the concept of 'template' binding in Knockout JS. The 'template' binding is used to render content based on a template defined elsewhere in the HTML or within the view model.
Example:
; ; var viewModel = { person: { name: 'John' } };
Ques 15
What is the purpose of the 'attr' binding in Knockout JS? The 'attr' binding is used to set or remove one or more attributes of an HTML element based on the value of the associated observable or expression.
Example:
; var viewModel = { imageUrl: 'path/to/image.jpg', imageAlt: 'Image Alt Text' };
Ques 16
How can you handle key events in Knockout JS? You can use the 'event' binding to handle various events, including key events, on HTML elements.
Example:
Ques 17
Explain the 'css' binding in Knockout JS. The 'css' binding is used to apply or remove CSS classes to an HTML element based on the truthiness of the associated observable or expression.
Example:
; var viewModel = { isActive: ko.observable(true), isDisabled: ko.observable(false) }; 