JQuery Interview Questions and Answers

By | October 8, 2021

jQuery is a simple, minified, efficient, open-source JS library that has tons of features that simplifies tasks like traversal of HTML docs, modification, handling of events, visual effects such as animations, Ajax, and Document Object Model (DOM), and JavaScript development. It makes it much easier with a convenient Application program interface that works across many gateways. It is completely based on “Write less, do more.” Check Best JQuery Interview Questions and Answers. 

The goal of jQuery is to make it much more straightforward to use JS on any webpage. By Using jQuery we can Wrap the numerous lines of JS code into a procedure that you can call with one line of code.

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The Library of jQuery has the following specifications:

  • Managing of Dom/HTML
  • Managing of CSS
  • The event methods of HTML
  • The animations and Effects
  • Standard AJAX
  • Many Utilities

The Basic Purpose to use jQuery is, it is probably the most well-known, and also the most flexible. some of the well-known companies which adopted the use of jQuery are –

  1. Google
  2. Microsoft
  3. IBM
  4. Netflix

To start using jQuery on your website, there are two ways.

  1. From jQuery.com we can import the jQuery library.
  2. Include jQuery from Content Delivery Network like Google.

There are two types of different categories of jQuery available for transferring to your web pages:

  1. Product category – This is for live websites because it has been compressed and zipped.
  2. Expansion category – This category is mainly used for testing and development of uncompressed and readable code.

The above versions can be transposed from jQuery.com.

Skills Required For Understanding jQuery:

  1. Command in JS, and workarounds.
  2. Powerful understanding of features and utility functions of jQuery.
  3. Fundamental understanding of web markup which probably includes HTML5 and CSS3.
  4. Standard ability approach to well-implemented custom jQuery plugins.

By understanding a few of the well-known jQuery interview questionnaires, you can gain maximum confidence in your job interview. We will discuss a set of general and complex questions asked by many interviewers.

Top jQuery Interview Questions and Answers

1. Explain jQuery in brief?

Answer: jQuery is a well-organized, quick JavaScript library that was built in the year 2006 by John Resig. The motto is to write less and do a lot more. So this is a quick and brief JS library that simplifies the traversing of HTML documents, handling of events, animating, and Ajax interactions for quick development of the web.

jQuery is a part of the JS toolset that is designed to minimize various tasks by writing shortcodes. It has gained quite a lot of popularity because it just needs you to write a simple code and it’s easy to understand which also makes your work with JavaScript easier.

2. Explain different features of jQuery?

Answer: jQuery has Offered a simple technique to pick the Dom elements, walk along with them, and manage their content by using a Sizzle which is a free, cross-browser open source selector engine. Now some of the other core features also include:

Event Handling: So, jQuery offers a well-defined way to pick a wide variety of events such as a user can click on a link without the assistance to clutter the code of HTML. So it becomes pretty easy, all you have to do is just click on any particular link to go to any other website or perform any sort of event it handles.

Ajax support: Well there’s also Ajax support. So jquery helps you in many ways to develop a reactive and feature-enrich site using the technology of ajax. It comes with plenty of implanted visual effects which you can use in your websites.

Lightweight: jQuery is a very Thin library. So, it is about 19 KB that is unified and unzipped, so it becomes pretty easy to use or install it and it does not take up much space. There are many other consequences that make jQuery so popular i.e, it has cross-browser support and works well in Safari, Chrome, and Opera, etc. These were some of the features of jQuery that make you believe that it is one of the best libraries of JavaScript.

3. What are the Benefits of jQuery?

Answer: The advantages of jQuery are –

  1. There is no above in learning any new syntax if you know JavaScript.
  2. It also can retain the code uncomplicated, readable, clear, and reusable.
  3. Cross-browser support.
  4. No composite loops and Scripting of DOM Library Calls.
  5. Detection and handling of events.

4. Name the latest version of jQuery.

Answer: The latest version of jQuery is 3.6.0, released on March 2, 2021.

5. Describe selectors in jQuery?

Answer: You can use jQuery selectors to select and edit HTML elements (s). Selectors in jQuery are used to select HTML elements depending on their name, id, classes, styles, attributes, attribute values, and other criteria. It makes use of existing CSS selectors and also some specific selectors of its own.

6. How many types of selectors are there in jQuery?

Answer: You can see that you have three main types :

  1. Tag name
  2. ID
  3. Class

Tag Name:

The name of a tag that is available in the DOM. $(‘div’) selects all div sections in the document

Syntax: $(‘div’ )

TagID:

Represents a tag in the DOM which has the given ID.
For example, $(‘#some-id’) selects the document’s single element with the ID some-id.

Syntax: $(‘#TextId’)

TagClass:

In the DOM, this represents a tag with the specified class. $(‘.some-class’), for example, selects all elements in the document with the class some-class.

Syntax:$(‘.myclass’)

So, these are the different types of selectors that are used in jQuery

7. Define jQuery .noconflict?

Answer: jQuery no-conflict is a jQuery choice for resolving conflicts between various javascript libraries or frameworks. When you make use of jQuery’s no-conflict mode, you change $ to a new variable and grant jQuery access to other libraries of JavaScript. Also, $ can be used as a jQuery subroutine or name of a variable.

8. What are the Ajax functions available in jQuery?

Answer: Ajax gives permission to the user to interchange the data with the server and eventually allows the users to update parts of a page without reloading the entire page so now there are various functions available :

  1. $.ajax(): This is considered to be the most basic level of functions, so we use this function to send the requests, and also we can use this function without any selector.
  2. $.ajaxSetup(): The setup function is used to set the various options for various Ajax objects.
  3. $.get.JSON(): This is an important unique type of function, used to allow the URL to which the requests are sent.

9. What are the several methods used to deliver the effects?

Answer: With jQuery, you can build up a nice website that is user-friendly and interactive. Now, to make it user-friendly and interactive, you need to add certain effects or you need to make it dynamic. So, jQuery provides many amazing effects like hiding, showing, toggling, fadeout, fade in, fade too, and a lot more.

Few methods descriptions are:

  • animate(params,[durations,easing,callback]):

This function makes user-defined animations for elements of HTML. You can add parameters such as your duration, easing, callback, or whatever animation you want to add inside your code. You achieve it with the help of the above-mentioned method. On the other hand, you can even have your own customized animations for all HTML elements.

  • fadeIn(speed,[callback]):

We also have the fadeIn method. Now, this function fades in all the elements which are matched just, by adjusting their opacity and firing an optional callback. After completion, you can also define these speeds and also call the callback function. This allows you to select any particular elements and those elements will be matched and then you can see the fade-in effect in them as well.

  • fadeOut(speed,[callback]):

We have the fade-out method which is used to fade out all the elements matched by modifying their opacity to zero. Then by adjusting the display to none and firing an optional callback again after completion. You can see the fade-out effect over there for the selected elements.

  • fadeTo(speed,opacity,callback):

The fadeTo function will fade the opacity of all the masked elements to a particular opacity.

  • stop([clearQueue,gotoEnd]):

This function halts all the currently executing animations.

10. What is .empty() versus .remove() versus .detach() in jQuery ?

Answer: All these look Similar but there are slight differences in all three of them. These are explained below:

  1. .empty(): This method is used to pull out the complete number of child elements from equally matched elements.

Syntax : $(selector).empty();

  1. .remove(): The empty method was only used for your child elements but the remove method is used for all your matched elements

Syntax: $(selector).remove();

  1. .detach(): This method is the same as remove, it will remove all other elements apart from any of your jQuery data

Syntax: $(selector).detach();

11. What exactly is the jQuery.holdReady() function?

Answer: We can use jQuery.holdReady() to hold, on the other hand, it can use d to release the execution of jQuery’s ready event.

This method must be called before the execution of a ready event. To postpone the ready event, use jQuery.holdReady(true). we must use jQuery.holdReady(true);, when we want to release the ready event, This type of function is useful when we want to fill a jQuery plugin before the ready event or when we want to perform certain events/functions before the document.ready() executes.

12. Can you point out the differences between live(), bind(), and delegate() in-built methods in JQuery?

Answer: The bind() method doesn’t really add events to elements that are appended after the DOM has been filled. The live() and delegate() methods, on the other hand, often bind events to future elements.

The live() method differs from the delegate() method in that it does not allow chaining. Only an element or a selector will be affected. However, the delegate() method may be used in a sequence.

13. Discuss the various cases in which jQuery could be used effectively?

Answer: jQuery is a versatile library framework that’s also extensively used in the following circumstances –

  1. Static or dynamic CSS functions may be used.
  2. Use events to call features.
  3. It’s for the sake of convenience.
  4. To create various animation effects.

jQuery is the best at sustaining different services with a higher degree of efficiency, due to the inclusion of all specialized library applications.

14. In jQuery, what’s the contrast between an ID selector, Class selector?

Answer: It is the same as what we do in CSS. Both the ID and Class selectors are used for the same work. In order to explain the working of both the concepts in simpler terms, The In cases when you need to select a unique element, then we have to go with the ID selector. And if you want to select a group of elements, then we have to go with the class selector.

15. What is the purpose of jQuery.data method?

Answer: The jQuery.data methods are associated with data with DOM nodes and DOM objects. This data method clarifies and condenses the jQuery code.

16. What is a Content Delivery Network (CDN)?

Answer: The term “Content Delivery Network” refers to the plan of a content delivery network. In general, a CDN is a broad network of computers spread through many data centers across the internet. The basic target of a CDN is to provide high availability and quality of network to end-users while delivering content.

17. What are the Comforts of using a CDN?

Answer: In terms of jQuery’s working functionality, CDN brings a lot of benefits to jQuery and provides a greater degree of effectiveness.

The CDN has a series of benefits like:

  1. Your server’s load is drastically decreased by using a CDN.
  2. The CDN saves bandwidth, helping jQuery to load faster than normal.
  3. The CDN’s most prominent feature is that it caches each jQuery-based website that a user visits.

18. How can we troubleshoot jQuery?

Answer: There are two methods for debugging jQuery:

  1. Debugger Keyword.
  2. The tool named debugger should be applied to where we want to initiate debugging and then use the F5 function key to launch Visual Studio in the same mode. After appending the procedure, add a breakpoint.

19. What’s the distinction with onload() and document.ready()?

Answer: The main takeaway between onload() and document.ready() is that onload() returns a value.

A page may only have one onload function at a time, in which all other onload functions will be terminated.

If it comes to the document.ready function, a page can have several document.ready() functions. Also, the onload function is called only when the DOM elements are packed on the tab, while the document.ready() function is called when the DOM is loaded.

20. What is the sense of the word “grouping”?

Answer: Grouping is an option in jquery by which it is used to group the data together. The process of grouping is explained below with an example:

  1. Set the groupable option to true to allow grouping.
  2. As a consequence, the grid’s header now has a new area that allows the user to group Grid data by column.
  3. Desired columns can be dragged by the users to the grouping header to group the data by several columns.
  4. $(“#grid”) is a function that returns the number of rows and columns in a grid.

21. Does the call stop (true, true) differentiate from the finish method?

Answer: The.finish() method would be identical to the.stop() method (true, true).

  1. It aids in the clearing of the queue, allowing the animations to progress to their final state.
  2. It also causes all queued animations’ CSS properties to leap to their end values when using.finish().

22. What is the method for checking the data form of any jQuery variable?

Answer: The $.type(Object), is the built-in JavaScript type method that is used for checking the data form of any jQuery variable

23. Point out the contrasts of the concepts of .js and .min.js?

Answer: The jQuery library has two various forms:

  1. Development
  2. Production.

The deployment version is also called the minified version in other words.

Taking into account, the functionalities of the two files are much close to each other. Being in small size, the .min.js gets filled rapidly reducing the bandwidth.

24. Describe the method of using regular expressions for extracting a query string?

Answer: There are two methods to extract a query string with regular expressions:

  • String approach:

The simplest way to extract a query string is considered with regular expressions. The .replace() method is carried forward by using the functioning.

For instance,

var data = string.replace("http://localhost/view.php?,"");
  • Approach to the regular expression:

This is the most powerful way to extract a query string and you must make use of the pattern for searching between the strings.

25. How can a method be called in jQuery from code-behind?

Answer:

By using $.ajax, we declare a WebMethod.

26. What parameters for the jQuery Ajax method are used?

Answer: The JQuery Ajax method uses four various parameters, which are as follows:

  1. URL: In order to send the request, the URL must be perfectly written.
  2. Type: Specifies the analysis methodology (Get or Post).
  3. Data: Signifies the server information
  4. Cache: This indicates whether the browser should index the page.

27. What is the function parent() in jQuery?

Answer: Parent() means top-level elements, usually selected by the jQuery selector for the given HTML objects. The parent procedure is used to edit changes at the top level of an HTML object.

Example: The parent can be a paragraph containing a few elements of the list. The parent is generally used if an action is based on the element child or if a parent needs a different treatment.

Example

ready(document).function()
$("span").parent().css("display: block", "border: 1px solid red");
( );

28. How Email is Validated in jQuery?

Answer: Email can be validated using jQuery by assigning @ and following the email standards.

Example –

function validateEmail(sEmail) { 
 var filter = ^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;  
if (filter.test(sEmail))
 {       
return true;
  } 
else 
{       
return false;
}

29. What does the term toggle mean in jQuery?.Explain.

Answer: The toggle() method is a prominent type of method that is used to switch between the hide() and show() methods. It simplifies the attached multiple functions to get toggle for the elements that were selected. You can assume it, as showing the hidden elements while hiding the visible ones.

Syntax: $(selector).toggle(function)

30. How does $(window).load or $(document).ready differ?

Answer:

$(window).load:

The browser uses $(window).load to show that all assets on the page (such as images and videos) are loaded.

$(document).ready:

For loading the DOM object tree, $(document).ready is used.

31. How are the size and length differ in jQuery?

Answer: JQuery size() method usually returns the total number of elements that are present in the object. The same thing is done by the length attribute, however, it is slightly faster because we avoid an extra function call.

32. How can we select several elements in jQuery?

Answer: To select several elements by the element selector in jQuery –

  1. The $(‘element 1, element2, element 3,….’) is the syntax.
  2. You must specify the selector elements and select them in any document with the assistance of * elements.

33. How can we add or delete classes in a jQuery element?

Answer: jQuery comes equipped to add or remove dynamically CSS classes with two syntaxes –

  • addClass()
  • removeClass(). ​

The following forms of syntax can be used:

removeClass() syntax:

$("button").click(function(){
  $("p").removeClass("intro");
});

addClass() syntax:

addClass( "your class" );

34. Is it appropriate to include the JQuery file on both the pages of Master and Content?

Answer: No, if the Jquery file is added to the master list, we can go straight to the content page without having to add a reference to it.

This can be illustrated accordingly.

<script type="text/javascript" src="jQuery-1.4.1-min.js"></script>

35. In jQuery, how do we delete an HTML tag’s attribute?

Answer: In jQuery, the removeAttr() method may be used to take off an attribute from an HTML tag. This method can be used to remove single or many attributes from an entity.

The following operation can be used.

syntax: $ (selector).

 $(selector).removeAttr(attribute)

36. What’s a JQuery filter? Give a Clarification of the situation

Answer: In jQuery, the filter() process is used to filter elements from an array that passes a functional test. The technique does not modify the original collection or perform the functions without values. This method is used to filter all the items that do not satisfy the selected criteria.

37. How can two strings be concatenated with jQuery?

Answer: The strings can be combined with the ‘+’ operator to concatenate two strings in jQuery. However, you must follow the code sequentially. The strings are concatenated once finished. There are also some other options.

var a = 'Best Interview';
var b = 'Question';
var result = a + b;

38. How are we able to check whether or not an element is blank using jquery?

Answer: It can be checked in two ways:

Way 1:

if ($('#element').is(':empty'))
{
   //write your code here
}

Way 2:

if ( $('#element').text().length == 0 ) 
{
   // length is 0
}

39. What are the different jQuery methods for making an ajax request?

Answer:

  1. $.ajax() is used for async requests.
  2. $.ajaxsetup() is used to set the default value.
  3. For object transmission, use $.ajaxTransport().
  4. $.get() is a method for retrieving data.
  5. Handle custom solutions with $.ajaxPrefilter().
  6. $.getJSON() is a function that loads JSON data.

40. How do text() and HTML() differ in jQuery?

Answer: The text() method returns text within an element of HTML, while HTML() returns the whole HTML syntax. In other words, to manage the value, the text() method is used, and the HTML() method is used to manipulate the property or the object.

41. Is jQuery a client or server scripting language?

Answer: jQuery is a scripting language for clients.

42. Discuss the example of deleting class jquery?

Answer:

$("#buttonID").
click(function(){
    $("YOUR_TAG_OR_CLASS_OR_ID").
removeClass("YOUR_CLASS_NAME");
});

43. What is jQuery UI, exactly?

Answer: jQuery UI makes it possible for our apps to provide a cool user interface and animation in a shorter period. It’s a set of JavaScript plugins that include user interactions, effects, animations, widgets, and themes. jQuery is used to make APIs that are consistent and cohesive.

We can use this method to extend jQuery prototype objects. You can make all jQuery objects inherit any method you add by using the prototype object. Interactions can be used to apply simple mouse-based behaviors to any feature. The following are some examples of interactions:

  1. Easily dragged
  2. Disposable
  3. Adaptable
  4. Possibility to pick
  5. Organizable

44. Using jQuery, how do you remove a DOM Element?

Answer: To create a dynamic web page, we may want to delete entire child nodes and pull out DOM elements using jQuery. There are several methods for deleting DOM elements, and these are provided by jQuery.

The options are here:

  1. HTML()
  2. remove()
  3. empty()

45. What are some of the features of jQuery that are commonly used in web applications?

Answer: jQuery has several useful features, which includes –

  1. Event management,
  2. Ajax support,
  3. Animation effects.

The following is a list of jQuery’s most significant features.

  • Event Handling: It is a feature that was implemented by jQuery. You must first comprehend the event before you can begin managing it. Actions are events. This means we write the code that is executed when a user clicks on a specific area of the page or moves the mouse over a form element. There are many events that are embedded in jQuery, such as a user clicking on a button, moving the mouse over an element, and so on.
  • Support for Ajax: Ajax is a technology that allows you to update a segment of an internet domain without having to refresh the whole web page. For instance, if you add a search feature to your website similar to Google Search when you type text into the Search TextBox, the relevant text appears without having to reload the tab. It’s easy to do with Ajax Methods.
  • jQuery animations or jQuery Visual effects: jQuery has a large number of built-in animation effects that you can use in your websites. For instance, animation, display, and hide. The animate() function in jQuery is extremely useful.

46. What does jQuery.ajax method() do?

Answer: An AJAX (asynchronous HTTP) request is made using the ajax() process. It gives you a lot of control over the information you pass and the data you receive. It allows you to handle the call errors as well as the data if the ajax page call is successful.

The following is a list of jQuery’s essential parameters:

  1. Method: ajax()
  2. kind: Indicates the request’s type (GET or POST).
  3. URL: The URL to which the request should be sent.

47. Explain the contrast between Map and Grep in jQuery?

Answer:

  1. The $.map() method loops over every element which is in the array and modifies its value. $.map ( array, callback(elementOfArray, indexInArray) ) is the basic structure of Map().
  2. $. Grep() method returns a filtered array from an existing array using a filter condition.

48. What are jQuery plugins and how do we use them?

Answer:

Plugins are code snippets. It is a code written in a grade JS file in jQuery plugins. These files of javaScript contain jQuery procedures that can be used in conjunction with the jQuery library. Any form used in plugins must end with a semicolon (;). Unless otherwise stated, the method must return an object (jQuery).

As a result, a clean and compatible code is created. You can prefix the filename with jQuery, then the name of the plugin, and finally the extension.js. (Take, for instance, jquery.plug-in.js.) Instead of using $, we can connect the plugin directly to jQuery so that users can use a custom feature. We should always attach the plugin directly to jQuery rather than using $ so that users can use a custom alias via the noConflict() method.

49. In jQuery UI, what are the functions Draggable, Resizable, Selectable, and Sortable?

Answer: The only plugins that are available in the interaction part are draggable, droppable, resizable, selectable, and sortable.

  1. Draggable: It gives any DOM feature draggable functionality. Drag the draggable object around the viewport by clicking it with the mouse and dragging it. It makes every DOM element droppable, making it a target for draggable elements.
  2. Resizable: It allows you to resize any DOM feature. Select the bottom or right border using the mouse cursor and move it to the desired width or height.
  3. Selectable: This property makes a DOM element (or a bunch of elements) selectable. To pick objects, draw a box with your cursor. To make several non-adjacent choices, hold down the Ctrl key.
  4. Sortable: It allows you to sort a set of DOM items. When you click and drag an element to a different location in the chart, the other elements will change to suit. Sorting items share portable properties by default.

50. When do you use $(document).ready(function())?

Answer: The jQuery event $(document).ready(function()) fires when the DOM is fully filled and ready to be edited by script. The script can safely approach elements in the HTML page’s DOM at this point in the page loading process. This event is activated before all of the photos and CSS have been loaded completely.

51. Explain the slice() method in jQuery?

Answer: By specifying a range of indices, this method selects a subset of the matched elements.

In other words, It returns a list of DOM elements based on the value of a parameter (start, end).

syntax: ( start, end[Optional] )

Summary

To summarise of JQuery Interview Questions and Answers –

  1. jQuery is a Document Object Model (DOM) manipulation library at its heart. The Document Object Model (DOM) is a tree-structure representation of all the elements that make up a Web page. The syntax for searching, sorting, and manipulating these DOM elements is simplified with jQuery.
  2. For example, jQuery can be used to locate an element in a document that has a specific property (for example, all elements with an h3 tag), modify one or more of its attributes (for example, color, visibility), or make it react to an event (e.g. a mouse click).
  3. jQuery also offers an event-handling model that extends beyond simple DOM element selection and manipulation. The event assignment and event callback function specification are done in one step and one place in the code.
  4. jQuery also aims to include other commonly used JavaScript features (e.g. fade-ins and fade-outs when hiding elements, animations by manipulating CSS properties).
  5. It separates JavaScript and HTML. Rather than using HTML event attributes to call JavaScript functions, the jQuery library provides a simple syntax for adding event handlers to the DOM using JavaScript.
  6. As a result, it allows developers to keep JavaScript code separate from HTML markup. With features including “chainable” functions and shorthand function names, jQuery encourages simplicity and clarification.
  7. Cross-browser compatibility is eliminated with jQuery. Since different browsers’ JavaScript engines vary slightly, JavaScript code that works in one browser can not function in another. jQuery addresses all these inter-browser inconsistencies.
  8. It provides a reliable GUI that operates on every platform. New events, components, and methods can be easily added and then reused as a plugin.

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