Intermediate / 1 to 5 years experienced level questions
Intermediate / 1 to 5 years experienced level questions & answers
Ques 1. 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: ; JavaScript: var viewModel = { name: ko.observable('John') };
Ques 2. 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 3. 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:
Visible Content; var viewModel = { showElement: ko.observable(true) };
Ques 4. 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 5. 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 6. 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:
; var viewModel = { handleKeyPress: function(data, event) { console.log('Key pressed:', event.key); } };
Ques 7. 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:
Content; var viewModel = { isActive: ko.observable(true), isDisabled: ko.observable(false) };
Ques 8. What is the purpose of the 'foreach' and 'as' combination in Knockout JS?
The 'foreach' and 'as' combination is used to alias the variable name used to represent each item in an array when using the 'foreach' binding.
Example:
; var items = ko.observableArray(['Item 1', 'Item 2']);
Ques 9. Explain the purpose of the 'hasfocus' binding in Knockout JS.
The 'hasfocus' binding is used to bind an observable to the focus state of an element, allowing you to track and control focus programmatically.
Example:
; var viewModel = { isFocused: ko.observable(true) };
Ques 10. How can you handle submit events in Knockout JS?
You can use the 'submit' binding to associate a function with the submit event of a form element.
Example:
; var viewModel = { handleSubmit: function() { alert('Form submitted!'); } };
Ques 11. Explain the 'with' binding in Knockout JS.
The 'with' binding is used to change the context for descendant elements, allowing you to bind against a different object.
Example:
; var viewModel = { person: { name: 'John' } };
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