Top 50 most asked jQuery interview questions

Updated By: Shrey Reddy

jQuery Interview Questions


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



Founders of jQuery


jQuery was initially released on 26th August 2006 & author(s) of jQuery "John Resig".



Top Most Asked 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 the jQuery Ajax method?


  • URL
  • Type
  • Data
  • Cache



Q5 Which kind of functions does JavaScript support?


The functions can be either named or anonymous in JavaScript.


Q6 What is a jQuery selector?


A jQuery Selector is a function. Actually, jQuery is used to find the HTML elements by the selectors. Here some selectors are mentioned.


  • 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 return 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 used to distribute OR deliver some content 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:


  • Microsoft: jQuery from Ajax CDN
  • Google: jQuery from Google libraries API



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


  • onload(): 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 'jQuery.fx.off' property.



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


animate() function syntax


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



Q19 What is 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 but SIZE is used to find element existence, element value size in jQuery.
  • The LENGTH & SIZE both returns 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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