jQuery Interview Questions and Answers

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jQuery Interview Questions and Answers

Vinay Khatri
Last updated on September 23, 2022

    jQuery is one of the most important JS libraries. Thus, you should expect jQuery interview questions during a JS-based interview. jQuery is a simple, minified, efficient, and open-source JavaScript library that has tons of features that simplify tasks like traversal of HTML docs, modification and handling of events, visual effects, such as animations, Ajax, traversing Document Object Model (DOM) , and JavaScript development .

    It makes it much easier with a convenient API that works across many gateways. It is completely based on the “write less, do more” principle. The goal of jQuery is to make it much more straightforward to use JS on any webpage. By using jQuery, we can wrap numerous lines of JS code into a procedure that you can call with only one line of code.

    The basic purpose of using jQuery is to make coding in JavaScript simple. It is probably the most well-known and also the most flexible JS library. Some of the well-known companies that use jQuery are:

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

    There are two ways to use jQuery on your website:

    1. We can import the jQuery library from jquery.com.
    2. Include jQuery from a content delivery network like Google.

    There are two categories of jQuery available for transferring the JavaScript library 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 .

    Want to learn and hone your jQuery skills? You can get started here .

    Skills Required for Understanding jQuery

    1. Good workability in JS and workarounds.
    2. Fundamental understanding of web markup that includes HTML5 and CSS3.
    3. A good ability to implement custom jQuery plugins.

    By understanding a few of the well-known jQuery interview questions, you can gain maximum confidence in your job interview. We will discuss a set of commonly asked interview questions that you may expect in any jQuery interview.

    Top jQuery Interview Questions and Answers

    We have divided the set of jQuery interview questions into three levels, namely basic jQuery interview questions, intermediate jQuery interview questions, and advanced jQuery interview questions.

    Basic jQuery Interview Questions

    1. Explain jQuery in brief.

    Answer: jQuery is a well-organized and fast JavaScript library that was built in the year 2006 by John Resig. The motto of jQuery is to do more with less code. jQuery simplifies the traversing of HTML documents, handling of events, animating, and Ajax interactions for quick development of websites and web applications.

    jQuery is a part of the JS toolset that is designed to minimize various tasks by writing shortcodes. It has gained a lot of popularity because it just needs you to write less code. Moreover, it's easy to understand, which makes working with JavaScript easier.

    2. Explain different features of jQuery.

    Answer: jQuery offers a simple technique to pick the DOM elements, walk along with them, and manage their content by using Sizzle, which is a free, cross-browser, and open-source selector engine. Other core features of jQuery are:

    • Event Handling : jQuery offers a well-defined way to pick a wide variety of events, such as a user click. So, it becomes pretty easy to handle events using the JavaScript library. 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: Ajax support is also available in jQuery. It helps you in many ways to develop a dynamic and feature-rich site using AJAX. It comes with plenty of visual effects that you can use on your websites.
    • Lightweight: jQuery is a lightweight library. It is about 19 KB that is unified and unzipped. Thus, it becomes pretty easy to use and install without sacrificing too much space.

    There are many other features that make jQuery so popular. For example, it has cross-browser support and works well in Safari, Chrome, and Opera. These were some of the features of jQuery that make it one of the best libraries of JavaScript.

    3. What are the benefits of jQuery?

    Answer: The advantages of jQuery are:

    1. There is no difficulty in learning the jQuery syntax if you know JavaScript.
    2. It also can retain the code uncomplicated, readable, clear, and reusable.
    3. It offers cross-browser support.
    4. There are no composite loops and scripting of DOM library calls in jQuery.
    5. It offers the 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, class, style, attribute, attribute value, and other criteria. It makes use of existing CSS selectors and also offers some selectors of its own.

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

    Answer: There are three main types of jQuery selectors:

    1. Tag name
    2. ID
    3. Class

    1. Tag name It is the name of a tag that is available in the DOM. $('div’) selects all div sections in the document.

    Syntax: $(‘div’ )

    2. TagID It 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’)

    3. 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 frameworks and libraries. 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 the 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. These are the AJAX functions available in jQuery:

    1. $.ajax() : This is considered to be the most basic level of jQuery functions. We use this function to send the requests. Also, we can use this function without any selector.
    2. $.ajaxSetup() : The setup function helps to set many options for various Ajax objects.
    3. $.get.JSON() : This is an important and unique type of function. It allows 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, fade-out, fade-in, and fade-to. Some of the most popular jQuery methods to deliver the effects are:

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

    This function makes user-defined animations for elements of HTML. You can add parameters such as duration, easing, callback, or whatever animation you want to add inside your code. Also, you can even have your own customized animations for all HTML elements.

    • fadeIn(speed,[callback]):

    We also have the fadeIn method in jQuery. Now, this function fades in all the matching elements by adjusting their opacity and firing an optional callback. After completion, you can 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 fadeOut method that is used to fade out all the matching elements 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 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 jQuery function halts all the currently executing animations.

    10. What are .empty(), .remove(), and .detach() methods in jQuery?

    Answer: Although these methods seem similar, there are slight differences in all three of them:

    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 only works for child elements, but the remove method works for all the matched elements.

    Syntax: $(selector).remove();

    1. .detach(): This method is the same as remove, but 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 the jQuery.holdReady() function to hold 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 or functions before the document.ready() method 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 the 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. What are the best scenarios to use jQuery?

    Answer: jQuery is a versatile library that's also extensively used for:

    1. Adding static or dynamic CSS functions.
    2. Use events to call features.
    3. It's for the sake of convenience.
    4. To create various animation effects.

    jQuery is 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 difference between an ID selector and a 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. When you need to select a unique element, go with the ID selector, and if you want to select a group of elements, then go with the class selector.

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

    Answer: The jQuery.data method is 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. Explain 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 offers the following benefits:

    1. It decreases the server's load drastically.
    2. A CDN saves bandwidth, helping jQuery to load faster than normal.
    3. A CDN's most prominent feature is that it caches each jQuery-based website that a user visits.

    Intermediate jQuery Interview Questions

    18. How can we troubleshoot jQuery?

    Answer: There are two methods for debugging jQuery:

    1. Using the 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 difference between onload() and document.ready() methods?

    Answer: The main difference between onload() and document.ready() is that the former returns a value. A page may only have one onload function at a time, in which case 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 to group the data together. The following examples explain the process of grouping:

    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 for checking the data form of any jQuery variable.

    23. Point out the differences between .js and .min.js?

    Answer: The jQuery library has two forms:

    1. Deployment
    2. Production

    The deployment version is also called the minified version. Taking into account, the functionalities of the two files are much close to each other. Being small in 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 in jQuery:

    1. String approach

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

    var data = string.replace("http://localhost/view.php?,"");

    2. 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 to call a method in jQuery from code-behind?

    Answer: By using $.ajax, we can declare a WebMethod.

    26. Enlist the parameters of the jQuery Ajax method.

    Answer: The following are the four parameters that the JQuery Ajax method uses:

    1. URL : In order to send the request, the URL must be available.
    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 or not.

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

    Answer: Parent means top-level elements. Usually, the jQuery selector selects the top-level elements for the given HTML objects. The parent procedure allows editing changes at the top level of an HTML object. It 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 will you validate an email validate in jQuery?

    Answer: We can validate an email in 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?

    Answer: The toggle() method enables you 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 and $(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: $(document).ready is used for loading the DOM object tree.

    31. How do size and length differ in jQuery?

    Answer: In jQuery, the size() method usually returns the total number of elements that are present in the object. We can achieve the same result using the length() method. However, it is slightly faster because it avoids an extra function call.

    32. How can we select several elements in jQuery?

    Answer: To select several elements by the element selector in jQuery, you need to:

    1. Add $('element 1, element2, element 3,....') in 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 offers two syntaxes to dynamically add or remove CSS classes. These are:

    1. addClass()
    2. removeClass()

    1. addClass() syntax:

    addClass( "your class" );

    2. removeClass() syntax:

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

    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. For example:

    <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 helps to remove an attribute from an HTML tag. This method is useful for removing a single or many attributes from an entity. For example:

    S yntax: $ (selector).

     $(selector).removeAttr(attribute)

    36. What's a jQuery filter?

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

    37. How will you concatenate two strings in jQuery?

    Answer: With the ‘+’ operator, we can concatenate two strings in jQuery. However, you must follow the code sequentially.

    Code example :

    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: In jQuery, we have two ways to check whether an element is blank or not:

    Way 1:

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

    Way 2:

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

    Advanced jQuery Interview Questions

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

    Answer: The following are the different jQuery methods for making an ajax request:

    1. $.ajax() is for async requests.
    2. $.ajaxsetup() sets the default value.
    3. For object transmission, use the $.ajaxTransport() method.
    4. $.get() is a method for retrieving data.
    5. Handle custom solutions with the $.ajaxPrefilter() method.
    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 , the text() method manages the value, while the HTML() method manipulates the property or the object.

    41. Is jQuery a client or server scripting language?

    Answer: jQuery is a scripting language for clients.

    42. How to delete a class in jQuery?

    Answer:

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

    43. What is jQuery UI?

    Answer: jQuery UI makes it possible for 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. With jQuery, we can develop APIs that are consistent and cohesive. You can make all jQuery objects inherit any method you add by using the prototype object. To apply simple mouse-based behaviors to any feature, we can leverage interactions.

    The following are some examples of interactions:

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

    44. How do you remove a DOM element using jQuery?

    Answer: To create a dynamic web page, we may want to delete entire child nodes and pull out DOM elements using jQuery. The JS library provides several methods for deleting DOM elements. These are:

    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 that include:

    1. Event Handling: 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.
    2. Support for Ajax : Ajax is a technology that allows you to update a segment of a webpage without having to refresh the whole web page. For instance, if you add a search feature to your website similar to Google Search, and when you type text into the search box, the relevant text appears without having to reload the tab. It's easy to do with Ajax methods.
    3. jQuery Animations or jQuery Visual effects: jQuery has a large number of built-in animation effects that you can use on your websites. For instance, animation, display and hide. The animate() function in jQuery is extremely useful.

    46. What does the jQuery.ajax() process do?

    Answer: To make an AJAX (asynchronous HTTP) request, we use 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 list enumerates 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 difference between Map and Grep in jQuery?

    Answer:

    1. The $.map() method loops over every element that is in the array and modifies its value. $.map ( array, callback(elementOfArray, indexInArray) ) is the basic structure of Map().
    2. The $. 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. These are codes written in a grade JS file. These files contain jQuery procedures that we can use in conjunction with the jQuery library. Any form in plugins must end with a semicolon (;). Unless otherwise stated, the method must return an object (jQuery).

    jQuery plugins help to create clean and compatible code. You can prefix the filename with jQuery, then the name of the plugin, and finally the extension.js. (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 a draggable functionality. Drag the draggable object around the viewport by clicking it with the mouse and dragging it. It makes every DOM element draggable, 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. 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 the script. The script can safely approach elements in the HTML page's DOM at this point in the page loading process. This event activates 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, the .slice() 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: slice( start, end[Optional] )

    Key Takeaways

    1. jQuery is a DOM manipulation library at its heart. The Document Object Model is a tree-like representation of all the elements that make up a web page. jQuery simplifies the syntax for searching, sorting, and manipulating these DOM elements.
    2. jQuery also offers an event handling model that extends beyond simple DOM element selection and manipulation. We can perform the event assignment and event callback function specification in one step and one place in the code.
    3. The popular JS library also aims to include other commonly used JavaScript features (for instance, fade-ins and fade-outs when hiding elements and animations by manipulating CSS properties).
    4. It separates JavaScript and HTML. Rather than using HTML event attributes to call JavaScript functions, jQuery provides a simple syntax for adding event handlers to the DOM using JavaScript.
    5. jQuery allows developers to keep JavaScript code separate from the HTML markup. With features including "chainable" functions and shorthand function names, jQuery encourages simplicity and clarification.
    6. 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.
    7. jQuery provides a reliable GUI that operates on every platform. Also, it makes it easy for us to add new events, components, and methods and then reuse them as plugins.

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    FAQs


    When you appear for an interview for the job role of a JavaScript developer, front-end developer, or web developer, you can expect questions on jQuery.

    jQuery is a front-end JavaScript library that minimizes the need for writing extensive JavaScript code.

    No, you can learn jQuery within a day or two if you have a good understanding of HTML, CSS, and JavaScript. If not, we recommend you learn those three languages first.

    The prime motive of jQuery is to write less and do more. So, it requires you to write less and achieve more features. In addition, jQuery makes event handling, DOM manipulation, and AJAx more simple than JavaScript. As a result, developers find it easier to work with jQuery than JavaScript.

    With jQuery, you can develop AJAX-based applications.

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