Top 20+ jQuery Interview Questions

jQuery is a client-side well written JavaScript library; it is designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.

Founders & Original Released Info

jQuery was initialy released on August 26, 2006 almost 13 years ago; and the original author(s) of jQuery "John Resig".

jQuery interview question
jQuery Interview Questions

Q1- What is jQuery?

jQuery is a fast, lightweight, feature-rich client-side well written JavaScript library that makes HTML document traversal and manipulation, event handling, animation, and Ajax much simpler and faster BUT jQuery is not a programming language.

Q2- Where jQuery code is getting executed?

jQuery code is getting executed on a client browser.

Q3- How to use jQuery?

Actually, jQuery is the collection of JavaScript classes; if we want to use these classes on the web page then 1st we need to bind all JavaScript classes in '.JS' files after that just add the reference of this '.JS's file on the web page.

Q4- What are the parameters used for jQuery Ajax method?

  • URL
  • Type
  • Data
  • Cache

Q5- Which kind of functions JavaScript support?

The functions can be either named or anonymous in JavaScript.

Q6- What is a jQuery selector?

A jQuery Selector is a function, the jQuery used to find the HTML elements by the selectors. There are some selectors types mentioned below:

  • CSS OR Tag Name Selector
  • .Class Element Selector
  • #ID Element Selector
  • (*) Universal Selector
  • Attribute Selector
  • Multiple Elements Selector

Q7- What is the difference between JavaScript and jQuery?

JavaScript: JavaScript is an interpreted programming language.

jQuery: jQuery is a fast, lightweight, feature-rich client-side well written JavaScript library. jQuery is built by using JavaScript.

Q8- Which command will returns a version of jQuery?

$.ui.version: command will returns a version of jQuery.

Q9- What is the list of jQuery features?

  • DOM Manipulation
  • Cross Browser Support
  • Event Handling
  • Fast Execution
  • Ajax Support
  • Lightweight
  • Animations
  • Latest Technology Support

Q10- What is a CDN?

The CDN stands for Content Distribution Network (CDN). CDN is a large network of shared servers and it is use to distribute OR deliver some contents BUT the primary objective of a CDN is to offer content to end-users with both, high availability as well as high performance.

Q11- What are the types of CDN?

There are two types of CDN used in jQuery:

  1. Microsoft: jQuery from Ajax CDN
  2. Google: jQuery from Google libraries API

Q12- What is the onload() and document.ready() method?

onload(): The onload() method is called only once when DOM is loaded.

document.ready(): The document.ready() method is called when DOM is loaded as well as when the image is loaded.

Q13- How to select all elements using jQuery?

Just Use: $('*') to selects all elements available in a DOM.

Q14- What is the difference between jQuery UI and jQuery?

jQuery UI: jQuery UI is built using JavaScript, but upon jQuery.

jQuery: jQuery is the library; It is built on pure JavaScript.

Q15- What is the finish() function in jQuery?

The finish() function is used to stop all queued animations and thereon places all the element(s) in their final state.

Q16- Which is the slow selector in jQuery?

'CLASS' Selector is slower than 'ID' and other selectors in jQuery.

Q17- How to disable jQuery animation?

Disable jQuery animation by using jQuery '' property.

Q18- What is the animate() function syntax in jQuery?

animate() function syntax:
$(selector).animate({params}, [duration], [callback])

Q19- What are the difference between 'length' and 'size' in jQuery?


  • The length is much faster than size as the length is property and size as the method.
  • The length is used to find element existence, element value length.
  • The length is return the value in number.


  • The size is slower than length in jQuery.
  • The size is used to find element existence, element value size in jQuery.
  • The size is return the value in number.

Q20- What is jQuery UI?

jQuery UI is a set of user interface interactions, effects, widgets, and themes built on top of the jQuery JavaScript library that can be used to build interactive web applications.

Q21- How to test jQuery?

Very easy & efficient way to test jQuery by using QUnit.

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