home bytes articles jquery interview questions

Web Development

Top JQuery Interview Questions and Answers (2024)

Last Updated: 13th October, 2024

Jay Abhani

Senior Web Development Instructor at almaBetter

Prepare for your next interview with this guide to top jQuery interview questions and answers, covering basic and advanced topics for freshers and experienced.

JQuery is one of the most popular JavaScript libraries that simplifies HTML document traversal, event handling, animations, and AJAX interactions. It is still widely used in many projects, making it a crucial topic for web development interviews. Whether you're a fresher or an experienced professional, it's essential to be well-prepared with jQuery interview questions and answers. In this article, we’ll cover jQuery interview questions for freshers, experienced professionals, and advanced users to help you ace your next interview.

JQuery Interview Questions for Freshers

1. What is jQuery?

jQuery is a fast, small, and feature-rich JavaScript library designed to simplify the client-side scripting of HTML. It makes tasks like event handling, animation, and manipulation of HTML documents much easier and more efficient. With a motto of "write less, do more," jQuery allows developers to implement complex functionalities using minimal code.

Example:

// Without jQuery
document.getElementById('example').style.color = 'blue';

// With jQuery
$('#example').css('color', 'blue');

2. What are the key features of jQuery?

Some of the key features of jQuery include:

DOM Manipulation: Easy traversal and modification of HTML elements.
Event Handling: Simplified handling of events like clicks, key presses, etc.
AJAX Support: Simplified methods for making asynchronous HTTP requests.
Animations: Built-in functions for creating simple animations.
Cross-browser Compatibility: Works consistently across different browsers.
Chaining: Allows combining multiple actions in a single line of code.

3. How do you include jQuery in a project?

There are multiple ways to include jQuery in a project:

Using a CDN: A common way to include jQuery is by linking it from a Content Delivery Network (CDN).

Local Installation: Download jQuery from the official website and include it locally.

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

$(document).ready() is a jQuery event that executes when the DOM is fully loaded, which allows JavaScript to run as soon as the document is ready.

$(document).ready(function() {
console.log("DOM is ready");
});

window.onload triggers after the entire page, including images, scripts, and external resources, is fully loaded.

window.onload = function() {
console.log("Page is fully loaded");
};

Key Difference: $(document).ready() executes earlier than window.onload, making it a preferred choice for many developers when dealing with just the DOM.

5. What is the use of the $() function in jQuery?

The $() function is a shorthand for the jQuery() function. It is used to select and manipulate HTML elements.

Example:

// Select an element with id="example"
$('#example').css('color', 'red');

// Select all <p> elements
$('p').hide();

6. What is event delegation in jQuery?

Event delegation is a technique in jQuery that allows you to attach a single event handler to a parent element to manage events for its children, even those that are dynamically added.

Example:

$(document).on('click', '.dynamic-button', function() {
alert('Button clicked!');
});

In this example, even if .dynamic-button is added dynamically after the page load, the event handler will still work.

7. What are the different types of selectors in jQuery?

jQuery selectors are used to select HTML elements based on their id, class, tag, attribute, or relationship to other elements. Some common selectors include:

ID Selector: $('#id')
Class Selector: $('.class')
Tag Selector: $('tag')
Attribute Selector: $('[attribute=value]')

Example:

$('#example');   // Select element with ID 'example'
$('.button');   // Select elements with class 'button'
$('div');   // Select all <div> elements
$('[type="text"]'); // Select all input elements with type 'text'

8. Explain jQuery chaining.

Chaining in jQuery allows you to perform multiple actions on the same set of elements within a single statement, improving readability and performance.

Example:

$('#example').css('color', 'blue').slideUp(2000).slideDown(2000);

Here, the element with id example will have its color changed, then it will slide up and down in sequence.

9. What is the use of the hide() and show() methods in jQuery?

hide(): Hides the selected elements.
show(): Displays the selected elements.

Example:

$('#example').hide(); // Hides the element
$('#example').show(); // Shows the element

You can also pass arguments to these methods to add animation effects like fade-out or slide-up.

$('#example').hide('slow');
$('#example').show(2000);

10. Explain the difference between empty()****, remove()****, and detach() in jQuery.

empty(): Removes the child elements of the selected element but keeps the element itself.

$('#example').empty();

remove(): Removes the selected element and its child elements from the DOM entirely.

$('#example').remove();

detach(): Similar to remove(), but it keeps the data and event handlers associated with the removed elements, allowing you to reattach them later.

var elem = $('#example').detach();
$('body').append(elem); // Reattaches the element

JQuery Interview Questions for Experienced

11. What is the purpose of the ajax() method in jQuery?

The ajax() method in jQuery is used to perform asynchronous HTTP requests (AJAX). It allows developers to send and receive data from the server without refreshing the page.

Example:

$.ajax({
url: 'data.json',
type: 'GET',
success: function(data) {
console.log(data);
},
error: function(err) {
console.log('Error: ', err);
}
});

This is one of the more common jquery advanced interview questions, particularly for experienced developers.

12. How do you stop the event propagation in jQuery?

You can stop event propagation by using the stopPropagation() method. This is helpful in scenarios where you don't want an event to trigger handlers attached to parent elements.

Example:

$('#child-element').click(function(event) {
event.stopPropagation(); // Prevents the event from bubbling up
});

13. What is the each() function in jQuery?

The each() function in jQuery is used to iterate over a collection of elements, executing a function for each matched element.

Example:

$('p').each(function(index, element) {
$(element).css('color', 'blue');
});

This is a commonly asked question among jquery interview questions for freshers and is useful for manipulating multiple elements.

14. What is the animate() method in jQuery?

The animate() method allows you to create custom animations for CSS properties. Unlike show() or hide(), which provide predefined effects, animate() gives you more control over the animations.

Example:

$('#example').animate({
width: '50%',
opacity: 0.5
}, 2000);

15. What are jQuery plugins, and how do you create them?

A jQuery plugin is a reusable piece of code that extends jQuery’s functionality. You can create a plugin by extending jQuery’s fn object.

Example:

$.fn.changeColor = function(color) {
return this.css('color', color);
};

// Usage
$('#example').changeColor('green');

16. What is the data() method in jQuery?

The data() method is used to store arbitrary data associated with DOM elements, making it easier to manipulate data without modifying the DOM structure.

Example:

$('#example').data('key', 'value'); // Store data
console.log($('#example').data('key')); // Retrieve data

17. How do you use fadeIn() and fadeOut() in jQuery?

fadeIn(): Gradually shows a hidden element by fading it in.
fadeOut(): Gradually hides an element by fading it out.

Example:

$('#example').fadeIn(1000);
$('#example').fadeOut(1000);

18. How do you bind multiple events to a single element in jQuery?

You can bind multiple events to an element using the on() method. This method can handle multiple events in one call.

Example:

$('#example').on('click mouseover', function() {
alert('Element clicked or hovered!');
});

19. Explain the serialize() and serializeArray() methods.

serialize(): Collects form data and encodes it in a query string format.

var formData = $('#form').serialize();

serializeArray(): Collects form data as an array of objects where each object contains name and value properties.

var formDataArray = $('#form').serializeArray();

20. How do you perform DOM manipulation in jQuery?

You can manipulate the DOM using methods like append(), prepend(), after(), and before() to add elements, and html(), text(), val() to set or retrieve content.

Example:

$('#example').append('<p>New Paragraph</p>'); // Adds inside element
$('#example').after('<p>Another Paragraph</p>'); // Adds outside element

Read Our Latest Blogs:

Differences Between JavaScript and jQuery
Vanilla JavaScript
JavaScript Cheat Sheet
Best Front End Frameworks

Conclusion

jQuery remains a vital tool for web development, widely used in both legacy systems and modern projects. Whether you're a fresher aiming to build a strong foundation or an experienced professional looking to demonstrate advanced expertise, mastering jQuery is a crucial skill for many web development roles. In this article, we've explored a comprehensive list of jQuery interview questions and answers, covering everything from basic jQuery interview questions to more advanced jQuery interview questions.

For freshers, it's important to focus on understanding the core concepts such as DOM manipulation, event handling, and selectors. On the other hand, experienced professionals should be ready to answer more complex queries on topics like AJAX, event delegation, and performance optimization.

By preparing thoroughly with these jQuery interview questions for experienced professionals and freshers, you can confidently demonstrate your knowledge and problem-solving skills during your interview. Whether you're handling basic interview questions or tackling advanced scenarios, a strong grasp of jQuery will set you apart in the competitive job market.