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30+ jQuery Interview Questions And Answers

jQuery is a fast, small, and feature-rich JavaScript library. It simplifies things like HTML document traversal and manipulation, event handling, and animation. It's widely used due to its simplicity and ease of use. jQuery also helps make websites interactive and user-friendly. Below are curated interview questions that range from beginner to advanced levels to assess a candidate's knowledge in jQuery.


Most asked jQuery interview questions



What is jQuery?

jQuery is a JavaScript library designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax. It's free, open-source software using the MIT License.


How do you add jQuery to your web project?

You can add jQuery to your web project by including the jQuery library in your HTML. This can be done either by downloading the jQuery library and linking to it locally or by linking to a CDN-hosted version.

<script src='' integrity='sha256-/xUj+3OJU5yEx1q6GSYGSHk7tPXikynS7ogEvDej/mw=' crossorigin='anonymous'></script>


Can you name some jQuery methods you have used?

Some common jQuery methods include .css() for applying style changes, .click() for click events, .hide() and .show() for visibility control, and .ajax() for asynchronous HTTP requests.


What is the difference between .get() and .eq() in jQuery?

The .get() method retrieves the DOM elements matched by the jQuery object as a plain JavaScript array. The .eq() method reduces the set of matched elements to one at a specified index.


What does $(document).ready() function do?

The $(document).ready() function ensures that your code runs only after the DOM has fully loaded, making it a safe place to hook up events and run other jQuery code.


What does this code do: $('#element').hide();?


This code selects the HTML element with the id 'element' and applies the .hide() method, which makes the element invisible on the page.


Is jQuery a library for client scripting or server scripting?

jQuery is a library for client-side scripting, which is used to enhance and manipulate the web page that runs in the user's browser.


How can you stop the default action of an element from occurring in jQuery?

You can stop the default action by calling the .preventDefault() method on the event object passed into your event handler.


What is chaining in jQuery?

Chaining in jQuery refers to the process of connecting multiple methods, one after the other, on the same set of jQuery objects. It's a powerful way to simplify your code and reduce redundancy.


How do you check which version of jQuery your web page is using?

You can check the version of jQuery used by your web page by typing $.fn.jquery or jQuery.fn.jquery in your browser's console.


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

The .each() function is a generic iterator function in jQuery that allows you to loop over a set of elements and apply a function to each one.


How do you select all anchor tags with a specific class in jQuery?

To select all anchor tags with a specific class, you can use the selector 'a.className'. Replace 'className' with the actual class name.


Explain the .animate() function in jQuery.

The .animate() function in jQuery allows you to create custom animations by modifying a set of CSS properties of an element over time.


What is the difference between '==' and '===' in jQuery?

The '==' operator checks for equality of value, but not type, while the '===' operator checks for both equality of value and type.


What is the purpose of method?

The method allows you to associate data with, or retrieve data from, DOM elements without affecting the DOM itself or the appearance of the document.

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Explain how 'this' works in jQuery callbacks.

Within jQuery callback functions, 'this' typically refers to the raw DOM element upon which the event was triggered, letting you act directly on the element without additional selector logic.


What is event bubbling and event capturing in jQuery?

Event bubbling and event capturing are two phases of event propagation. In event bubbling, the event starts from the target element and bubbles up the DOM tree. In event capturing, the event starts from the outermost element and travels down to the target element.


How can you optimize jQuery selectors for performance?

To optimize jQuery selectors for better performance, you should use ID selectors when possible, scope your searches within a parent element, and minimize the use of universal and multiple selectors.


What is the promise/deferred object in jQuery?

A promise/deferred object in jQuery represents an operation that hasn't completed yet but is expected in the future. It allows you to attach multiple callbacks and control the flow of deferred activities.


What is the purpose of jQuery's .map() method?

jQuery's .map() method applies a function to each item in the original set and constructs a new jQuery array from the values returned by that function.


How can you create a deep copy of an object in jQuery?

You can create a deep copy of an object using the jQuery.extend(true, {}, myObject) method, which performs a deep merge, recursively copying properties from the source object to a new object.


Discuss jQuery's AJAX methods and how they differ.

jQuery offers several AJAX methods, like $.ajax(), $.get(), $.post(), and $.load(). The $.ajax() method is the most versatile, offering customization for complex requests. The other methods offer shorthand for common use cases.


How do you prevent multiple events from firing in jQuery?

To prevent multiple events from firing, you can use .off() to unbind previous event handlers before binding new ones or .stopPropagation() to prevent event bubbling up the DOM tree.


What is the use of the .done(), .fail(), and .always() methods in jQuery's AJAX call?

The .done() method is called when an AJAX call succeeds, .fail() is called upon failure, and .always() method is called regardless of the success or failure of the request.


Can you demonstrate a custom jQuery selector?

$.expr[':'].customSelector = function(elem) {
  return $(elem).text() === 'Custom Text';

A custom jQuery selector can be created by extending the $.expr object with a function that defines the custom behavior. This function should return true for elements that match the custom criteria.


How do you create a toggle function in jQuery?


A toggle function in jQuery can be created by using the .toggle() method inside a click event handler. The method alternates hiding and showing the matched elements.


What does 'event delegation' mean in jQuery?

Event delegation refers to the process where the parent element listens for events and handles them on behalf of child elements that match a specified selector. It's useful when dealing with dynamically added elements.


Explain the difference between .bind(), .live(), and .on() methods in jQuery.

.bind() attaches event handlers to the current matched elements; .live() was used to attach event handlers to all elements matching a selector now and in the future (deprecated in jQuery 1.7); .on() is the preferred method that combines and improves the functionality of both .bind() and .live().


How can you detach an event handler in jQuery?

You can detach an event handler using the .off() method. This method can remove event handlers that were attached with .on().


Can you explain how to chain AJAX requests in jQuery?

You can chain AJAX requests by using jQuery's Deferred objects and the .then() method that allows for specifying callbacks for progressing actions as responses are received.


jQuery Interview Tips

Understand the Job Requirements

  • It's crucial to understand the skills and knowledge the job requires. Take time to go through the job specs and match them with your experience and strengths. Be clear on examples that showcase your skills relevant to jQuery development. Knowing what the employer needs ensures you focus on pertinent examples during the interview.

Focus on Clarity and Simplicity

  • When answering tough questions, clarity and simplicity are paramount. Avoid jargon unless absolutely necessary; focus on breaking down complex ideas into easily digestible parts. If you need to use technical terms, briefly explain them to demonstrate your proficiency and help your interviewer understand your reasoning process.

Stay Calm and Confident

  • Keeping a calm demeanor helps convey confidence. When faced with a difficult question, pause for a moment, gather your thoughts, and give a considered response. Remember, it's better to think before speaking than to give an immediate but misguided answer.

Structured Thought Process

  • Approach each question with a structured thought process. For technical queries, start by defining the problem, outline the steps to solve it, and finish with a solution backed by reasoning. This approach demonstrates a systematic methodology to problem-solving, an attractive trait for developers.

Use Examples to Showcase Your Skills

  • Using specific examples from your experience can turn a tough question into an opportunity to shine. Prepare a range of examples that cover different scenarios, such as problems you’ve solved, successful projects, and challenging situations where you found creative solutions. Make sure some of these examples include your jQuery work to demonstrate your practical knowledge of the library.


Where can I hire a JavaScript developer?

Look no further than FireHire for hiring top-tier JavaScript developers with a broad range of technical proficiencies. Read more: Where can I hire a JavaScript developer?

Who is the developer of jQuery?

jQuery was originally created by John Resig and is maintained by a team of developers from around the world. Read more: Who is the developer of jQuery?

What is the job description of jQuery?

A jQuery developer specializes in using the jQuery library to build dynamic and accessible user interfaces, optimizing interactivity and performance of web applications. Read more: What is the job description of jQuery?

Why using FireHire for hiring jQuery developers is the best choice?

Choosing FireHire gives you access to pre-vetted senior jQuery developers, rapid placement services, and a 30-day risk-free replacement guarantee — all at competitive costs starting from $45/hour.

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