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Interview Questions for JQuery

Interview Questions for JQuery

Basic JQuery Interview Questions

1. What is JQuery?

JQuery is a fast and lightweight JavaScript library that simplifies tasks like HTML document traversal, manipulation, event handling, and AJAX.

2. How do you include JQuery in a project?

You can include JQuery by adding a <script> tag in the HTML file linking to the JQuery CDN or a downloaded JQuery file. For example:

3. What is the $ symbol in JQuery?

The $ symbol is an alias for the JQuery function. It is a shorthand way to call JQuery methods.

4. How do you detach events in JQuery?

The .off() method is used to remove event handlers that have been attached with .on().

5. What is the difference between $(document).ready() and window.onload?

The $(document).ready() function in JQuery is executed when the DOM is fully loaded, but before other resources like images and CSS are completely loaded. On the other hand, window.onload waits for all resources, including images and CSS, to be loaded before executing the code.

6. Can you explain the this keyword in the context of JQuery?

In JQuery, the this keyword refers to the DOM element that is currently being acted upon in the event handler. It allows you to perform actions on the element without having to reselect it.

7. What are selectors in JQuery? Can you provide some examples?

Selectors are patterns used to match DOM elements. For example, $('p') selects all paragraph elements, and $('.className') selects all elements with the given class name.

8. What are the different types of selectors in JQuery?

JQuery supports a wide range of selectors including ID selectors (#id), class selectors (.class), element selectors (element), and more advanced selectors like attribute selectors and pseudo-selectors.

9. How do you perform event binding in JQuery?

You can use methods like¬†.click(),¬†.bind(),¬†.on(), etc., to bind events to elements. For example,¬†$('#button').click(function() { /* code */ });¬†binds a click event to an element with the ID of ‚Äėbutton‚Äô.

10. What are the main differences between JavaScript and JQuery?

JavaScript is a programming language, whereas JQuery is a library built on top of JavaScript. JQuery simplifies tasks such as DOM manipulation and event handling, making it easier and faster to develop web applications.

Advanced JQuery Interview Questions

11. How do you make an AJAX call using JQuery?

You can use the $.ajax() method to make AJAX calls. It allows you to specify options like the URL, data type, and success and error callbacks.

12. Explain the animate() method in JQuery.

The animate() method allows you to create custom animations. You can animate CSS properties over a specified duration.

13. How do you traverse the DOM using JQuery?

JQuery provides various traversal methods like .parent(), .children(), .next(), .prev(), etc., to navigate through the DOM.

14. What is chaining in JQuery?

Chaining allows you to execute multiple JQuery methods on the same set of elements, in a single line. For example, $('p').hide().addClass('hidden').fadeIn();

15. How do you add or remove elements dynamically using JQuery?

You can use methods like .append(), .prepend(), .remove(), and .empty() to add or remove elements.

16. What is the use of the data() method in JQuery?

The data() method allows you to attach data to, or fetch data from, DOM elements. This can be useful for storing additional information without modifying the DOM.

17. How can you hide or show elements using JQuery?

You can use methods like .hide(), .show(), or .toggle() to hide, show, or toggle the visibility of elements.

Interview Questions on jQuery for Experienced

18. What are JQuery plugins and how do you use them?

JQuery plugins are reusable pieces of code that extend the functionality of JQuery. You can use a plugin by including its JavaScript file after including the JQuery library.

19. What are the advantages and disadvantages of using JQuery?

  • Advantages: Easy to use, large community, lots of plugins, simplifies complex tasks like AJAX and DOM manipulation.
  • Disadvantages: Adds to page load time, may lead to over-dependency, not always necessary for simple tasks.

20. What are some common JQuery methods used for form validation?

Methods like .val(), .prop(), and .attr() can be used to get or set the values and attributes of form elements. You can also use .submit() it to handle form submissions.

21. How do you get or set attributes using JQuery?

The .attr() method can be used to get or set attributes. For example, $('img').attr('src', 'image.jpg') sets the source attribute of an image element.

22. Explain the each() method in JQuery.

The each() method is used to loop through elements in a JQuery object. It allows you to apply the same set of actions to all elements in the selection.

23. What is event delegation in JQuery?

Event delegation allows you to attach a single event listener to a parent element, which will fire for all descendants that match a given selector. This is useful for elements that are dynamically added to the DOM.

24. What is the difference between .bind(), .live(), and .on() methods for event handling?

.bind(): Attaches events to elements that are currently in the DOM.

.live(): Deprecated method that is used to attach events to current and future elements in the DOM.

.on(): Replaces both .bind() and .live(), and can be used for attaching events to current and future elements.

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