For those preparing for an upcoming jQuery interview, it’s important they are familiar with the all of its features and functions. It should go without saying that a strong JavaScript developer should be familiar with jQuery because, in a way, they both go hand in hand.

We’ve compiled a list of 70 jQuery interview questions to get you more than ready for your upcoming interview and closer to landing your next freelance developer contract.

These questions are designed with the goal of getting readers acquainted and familiar with the type of questions they may encounter during an interview. It’s important to keep in mind that there is much more to getting hired than simply being able to answer tough technical questions.

jQuery_interview_questions

So, what is jQuery and why should you care?

For any web developer that is dabbling in JavaScript code — if it’s not already — jQuery should be implemented in your JavaScript coding routine. Most developers who are skilled in jQuery will already have a common knowledge of HTML, CSS, and yep, you guessed it, JavaScript.

jQuery_interview_questions

jQuery’s sole purpose is to make it easier for you to use JavaScript on your website. W3schools describes jQuery as a “lightweight, ‘write less, do more,’ JavaScript library.” Some of the biggest companies on the web use jQuery including Microsoft, Google, IBM, Netflix and more.

Not only is jQuery a time-saver but it also simplifies a great deal of aspects from JavaScript such as AJAX calls and DOM manipulation. jQuery takes these commons tasks that require several lines of JavaScript code and it wraps them into various methods that you can call on with a single line of code. How great is that?

jQuery_interview_questions

Why should you use jQuery?

As a web developer, you may already know that there are a handful of other JavaScript frameworks readily available out there, so why use jQuery? Not only is it one of the most popular frameworks but it is also the most extendable and versatile frameworks to work with. jQuery has ultimately changed the way people write JavaScript.

Here’s what jQuery is typically needed for:

  • used to develop browser compatible web apps
  • improve the performance of an app
  • fast and extensible
  • UI-related functions are written in minimal lines of codes

Types of jQuery Questions in this Study Guide:


General

1. What is jQuery?

 

>jQuery.com defines jQuery as “a fast, small, and feature-rich JavaScript library. It makes things like HTML document traversal and manipulation, event handling, animation and Ajax much simpler with an easy-to-use API that works across a multitude of browsers.”

 


2. Is jQuery a replacement of JavaScript?

 

No, jQuery is essentially built on top of JavaScript.

 


3. Why is jQuery better than JavaScript?

 

It depends. jQuery’s library used for developing Ajax support and applications but it also handles events, animation, and it helps to write clean and organised code. jQuery can be heavy and nowadays, we have a lot of lightweight libraries that provide support for separate projects. It’s better if users select the libraries they need for their work instead of using a bundle of libraries at one time.

 


4. What is the difference between jQuery and JavaScript?

 

It is important to note that JavaScript is a language and jQuery is a built-in library that is built of JavaScript. Ultimately, jQuery simplifies the use of JavaScript language. jQuery is written on top of JavaScript and it is essentially a different library.

 


5. Where can you download jQuery?

 

jQuery JavaScript can be downloaded from jQuery’s official website at jQuery.com.

 


6. Is jQuery a client or a server scripting?

 

jQuery is a client scripting.

 


7. Is jQuery a W3C standard?

 

No, jQuery is not a W3C standard.


8. What features of jQuery have been used in web applications?

 

jQuery uses features such as Sliding, File uploading and accordion in various web applications.

 


9. What are the core features of jQuery?

 

  • DOM Manipulation − jQuery makes it easier to select DOM elements, traverse them and modify their content by using a cross-browser open source selector engine called Sizzle.
  • Event Handling − jQuery offers a useful way to capture a wide variety of events, for example, a user clicking on a link, without the need to clutter the HTML code itself with event handlers.
  • AJAX Support − Allows you to develop a responsive and feature-rich site using AJAX technology.
  • Animations − jQuery comes with plenty of built-in animation effects that you can use throughout their websites.
  • Lightweight −  jQuery is a very lightweight library. It is about 19KB in size (Minified and gzipped).
  • Cross Browser Support − jQuery has cross-browser support which works well in IE 6.0+, FF 2.0+, Safari 3.0+, Chrome and Opera 9.0+.
  • Latest Technology − Supports CSS3 selectors and basic XPath syntax.

10. What is each function used to do in jQuery?

 

Each jQuery function is used to iterate every element of an object. The jQuery functions are used to loop DOM elements, arrays and object properties.

 


11. What are the advantages of jQuery?

 

  • It serves as a JavaScript enhancement.
  • It makes coding more simple, clear and reusable.
  • Easy removal of writing more complex conditions and loops.

 


12. In what scenarios can jQuery be used?

 

  • Apply CSS static or dynamic.
  • Calling functions on events.
  • Manipulation purposes.
  • Mainly for Animation effects.

 


13. What are the methods used to provide effects?

 

  • Show()
  • Hide()
  • Toggle()
  • FadeIn() and
  • <FadeOut()

 


14. What are the browser related issues for jQuery?

 

Some browser related issues that occur with jQuery include the browser compatibility of the jQuery plugin. This occasionally needs to be fixed.

 


15. What is the difference between the size and the length of jQuery?

 

Size and length both return the number of elements in an object. But length is faster than the size because length is a property and size is a method.

 


16. Is jQuery a JavaScript or JSON library file?

 

jQuery is a library of a JavaScript file and it consists of DOM, event effects and Ajax functions. jQuery is described as a single JavaScript file.

 


Anonymous Functions


17. Define an anonymous function.

 

An anonymous function is similar to a normal function but it does not have any name linked to it.

 


18. Is it possible to assign an anonymous function to a variable?

 

Yes.

 


19. Can you pass an anonymous function as an argument to another function?

 

Yes.

 


20. What are all the various ways to include jQuery in a page?

 

  • Local copy inside a script tag.
  • Remote copy of jQuery.com.
  • Remote copy of Ajax API.
  • Embedded script using client script object.

 


Selectors


21. Describe a jQuery selector.

 

A selector is a function that uses expressions to find out matching elements from a DOM based on the given criteria. They are used to select one or more HTML elements using jQuery. Once an element is selected, you can perform various operations on that selected element.

 


22. What types of selectors are in jQuery?

 

  1. CSS Selector
  2. XPath Selector
  3. Custom Selector

 


23. What are the basic selectors in jQuery?

 

  • Element ID
  • CSS Name
  • Tag Name
  • DOM hierarchy

 


24. Which is the fastest selector in jQuery?

 

ID and Element are the fastest selectors.

 


25. What is the slowest selector in jQuery?

 

Class selectors are the slowest selectors.

 


26. How do you resolve a conflict with another JavaScript library if $ is already in use?

 

The $() function is a synonym of a jQuery() function. If you are using another JavaScript library where $ sign conflicts, then you can replace the $ sign by its jQuery name and you can use the function jQuery() instead.

 


27. What is chaining?

 

Chaining is used to connect multiple events and functions in a selector.


28. What is jQuery connect?

 

A jQuery connect is a plugin used to connect a function with another function. jQuery connect is used to execute functions from any other function or plugin that is executed.


29. How do you use connect?

 

One can use connect by downloading a jQuery connect file from jQuery.com and by including it in the HTML file. Use the ‘$.connect’ function to connect a function to another function.

 


30. What is the difference between find and children methods?

 

Find method is used to find all levels down the DOM tree. Children methods are used to find single level down the DOM tree.

 


31. What is the use of jQuery filter?

 

The jQuery filter is used to filter certain values from the object list based on specific criteria. An example is to filter certain products from the master list of products in a cart website.

 


32. What is the use of jQuery.data() method?

 

jQuery data method is used to associate data with DOM nodes and JavaScript objects. This method is used often because it keeps your code very concise and organised.

 


33. What type of features does the jQuery library contain?

 

  • HTML/DOM manipulation
  • CSS manipulation
  • HTML event methods
  • effects and animations
  • AJAX
  • utilities

 


34. How do you make sure that DOM is already using jQuery?

 

Use $(document).ready() function. Everything inside it will load as soon as the DOM is loaded and before the page contents are loaded.

 


Elements


35. How do you select elements using jQuery with the given element tag-name?

 

$(‘tag-name’) selects all elements of a type tag-name in the document. For example, $(‘p’) selects all paragraphs in the document.

 


36. How do you get the html contents (innerHTML) of an element using jQuery?

 

The html() method gets the html contents (innerHTML) of the first matched element.

 


37. How do you get the width and how do you set the width of an element using jQuery?

 

The width( val ) method sets the CSS width of every matched element and the width( ) method gets the current computed, pixel, width of the first matched element.

 


38. How do you remove a set of matched elements?

 

The remove( expr ) method removes all matched elements from the DOM.

 


39. How can you create an Object in JavaScript?

 

JavaScript supports Object concepts extremely well. You can create an object using the object literal as displayed below

var emp = {
    name: "Zara",
    age: 10
};

40. What is the purpose of 'this' operator in JavaScript?

 

‘this’ is JavaScript’s famous keyword and it always refers to the current context.

 


41. Which sign is used as a shortcut for jQuery?

 

The Dollar ($) sign is used as a shortcut.

 


42. What is the advantage of using a minimised version of jQuery?

 

When a minimised version of jQuery is used, this makes your web page much faster.

 


43. What is the script build up by jQuery?

 

jQuery is a JavaScript file and its single javascript file contains common DOM, event effects and Ajax functions.

 


44. What program is most useful for testing jQuery?

 

QUnit is used to test jQuery and it is very easy and efficient to use.

 


45. How can you debug jQuery?

 

  1. Debugger Keyword- Add the debugger to the line from where you have to start debugging and then run a Visual Studio in Debug mode with your F5 function key.
  2. Insert a breakpoint after attaching the process.

 


46. Can jQuery HTML work for both HTML and XML documents?

 

No, jQuery HTML does not work for XML documents, it only works for HTML.

 


47. Is it possible to call C# code behind using jQuery?

 

Yes, you can use jQuery to send an Ajax request to the server to make a call to C# code.

 


48. What is jQuery.data method used to do?

 

The jQuery.data methods are used to associate data with DOM nodes and the objects. This data method is what makes jQuery code clear and concise.

 


49. What is CDN and what does it stand for?

 

CDN stands for Content Distribution Network and it is a group of different companies in multiple locations with networks containing copies of data files in order to maximise bandwidth in accessing the data.

 


50. What are the two types of CDNs?

 

  1. Microsoft – Load jQuery from Ajax CDN
  2. Google – Load jQuery from Google Libraries API

 


51. What are the advantages of using a CDN?

 

Using a CDN reduces the load on the server and it saves bandwidth because jQuery framework loads more quickly from these CDN. In addition, if a user visits a site regularly which is using jQuery framework from any of these CDN, it will be cached.

 


52. How do you include your jQuery library in an ASP.Net project?

 

Download the jQuery library from jQuery.com and include that reference in the asp.net page.

 


53. What is the difference between onload() and document.ready()?

 

We can have only one on-load function but we can have more than one document.ready function. Document.ready function is called DOM when it is loaded. The on-load function is called DOM and images are loaded on the page.

 


54. What built-in method combines the text of two strings and returns a new string?

 

concat() method returns the character at the specified index.

 


55. Which method is used to define the specific character in place of $ sign?

 

‘NoConflict’ method is used to reference a jQuery and save it in a variable. This variable can be used instead of Sign.

 


56. What built-in method calls a function for each element in an array?

 

forEach() method calls a function for each element.

 


57. What is the difference between the .detach() and the .remove() methods?

 

The .detach() retains all jQuery data associated with the removed elements and the .remove() does not. Apart from this distinction, they are the same. When removed elements need to be reinserted in the DOM later, this is when the .detach() is most useful.

 


58. Do we need to add a jQuery file in both the Master and Content pages?

 

The jQuery file should be added to the Master page and then it can be used or directly accessed from the content page without having any reference to it.

 


59. How do you get and set the style property of an element using jQuery?

 

The css( name ) method returns a style property on the first matched element as well as setting a single style property to a value.

 


60. How do you get and set the width of an element using jQuery?

 

The width( val ) method sets the CSS width of every matched element along with the current computed pixel.

 


61. What is the use of jQuery load method?

 

jQuery load method is a powerful AJAX method that is used to load the data from a server and assign the data to the element without loading the page.

 


62. Which method can be called inside code behind using jQuery?

 

$.ajax can be called and by declaring WebMethod inside code behind using jQuery.

 


63. How do you make an ajax call?

 

The load( url, [data], [callback] ) method load HTML from a remote file and inject it into the DOM.

 


64. Please explain the difference between a jQuery.get() and a jQuery.ajax()?

 

jQuery.ajax() is an all-encompassing Ajax request method. It creates customized Ajax requests, with options for response time, handling a failure for blocking (synchronous) or non-blocking (asynchronous) requests, formatting a request for the response, etc.

jQuery.get() is a shortcut method that uses jQuery.ajax() to create an Ajax request for simple retrieval of information. Other pre-built Ajax requests include jQuery.post(), jQuery.getScript(), and jQuery.getJSON().

 


65. Is it possible to add more than one ‘document.ready’ function in a page?

 

Yes, but it’s important to note that body.onload can only be added once it is on a page.

 


66. How can you create an Array in JavaScript?

 

You can define arrays using the array literal described below

var x = [];
var y = [1, 2, 3, 4, 5];

 


67. Can you use your own specific characters in place of $ in jQuery?

 

Yes, you can use your own variable in place of $ by using the method called no Conflict () method.

var sample = $.noConflict()

 


68. What built-in method returns the character at the specified index?

 

charAt() method returns the character at the specified index.

 


69. What are the four parameters used for the jQuery Ajax method?

 

The four parameters are:

  • URL – Need to specify the URL to send the request.
  • Type – Specifies type of request (Get or Post).
  • Data – Specifies data to be sent to the server.
  • Cache – Whether the browser should cache the requested page.

 


70. When do you use the jQuery.ajax method ()?

 

jQuery.ajax method is used for asynchronous HTTP requests.

 

 

We’d like to thank Nguyễn Chí Duy Đức for lending his jQuery expertise to this article.

Đức is our Senior Full Stack Developer. He is highly enthusiastic and a self-starter developer who is always striving to stay on top of the newest technologies.

 

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