Top jQuery Interview Questions and Answers

jQuery Interview Questions

What is jQuery?
Is jQuery a programming language?
How are JavaScript and jQuery different?
Is jQuery a replacement for JavaScript?
Why do we use jQuery?
What is $() in jQuery library?
Explain some effects methods used in jQuery?
Explain the use of the toggle() method in JQuery?
What is the main role of the fadeToggle() method in JQuery?
Explain the use of delay() method in JQuery?
Is jQuery HTML work for both HTML and XML document?
Tell us the use of html() method in JQuery?
Use of css() method in JQuery?
For what jQuery library is used for server scripting or client scripting?
Is jQuery a W3C standard?
At what point does the code execution in jQuery starts?
What is the requirement to start working with jQuery?
Is there any alternate name at the place of $ (dollar sign) in jQuery?
Are you able to use multiple document.ready() function on the same page?
Tell us the difference between the find method and the children method?
What is a CDN?
What is the main purpose of CDN and the advantages of using it?
How jQuery library can be used in your project?
What are the selectors in jQuery? How many types of selectors in jQuery?
What is the use of jQuery filters?
How many types of selectors are there in jQuery?
Explain the difference between the ID and class selector in jQuery?
Tell the use of the serialize() method in JQuery?
How val() method is used in JQuery?
How can you add or remove CSS classes to an element using jQuery?
Write a jQuery code in which you select all links inside the paragraph?
Differentiate between prop() and attr()?
Name two types of CDNs?
Tell me the use of the animate() method in jQuery?
How do you disable jQuery animation?
Is jQuery a JavaScript or JSON library file?
What are events in jQuery?
What is the use of jQuery.length method?
What is a jQuery click event?
How to perform jQuery AJAX requests?
What does the following code do?
$( “div#firstDiv, div.firstDiv, ol#items > [name$='firstDiv’]” )
What does the following code do
$( “div” ).css( “width”, “500px” )
.add( “p” )
.css( “background-color”, “yellow” );
Tell difference between jQuery.get() method and jQuery.ajax() method?
In the following given codes which is more efficient and why? document.getElementById(“jobinterviewninjas”); OR $("#jobinterviewninjas”);
Write a jQuery code selector which will query all elements whose ID ends with the string “IB”?
Explain the .promise() jQuery function.
How between prop() and attr()s are different?
What is JQuery.noConflict?
What is jQuery UI?
How to handle Controls attribute Using jQuery?
What is chaining in jQuery?
How parent(), children() and siblings() methods works in jQuery?
Explain bind() elements and unbind elements in jQuery?
How to remove a DOM element using jQuery?
What is the use of a jQuery filter?
What is the use of jQuery.ajax method()?
What is an attribute in jQuery?
What are jQuery Events?
How are you able to find browser and browser versions in jQuery?
Tell us the difference between Map and Grep functions in jQuery?
What are jQuery plugins?
What is jQuery.holdReady() function?
What is resize() function in jQuery?
Tell the use of Draggable, Droppable, Resizable, Selectable in jQuery UI?
Tell us the history & uses of jQuery UI?
Define jQuery UI Autocomplete?
What do you understand by jQuery UI Sortable and how to use it?
Why use the jQuery $ sign?
What is slice() method in jQuery?
What is queue() in Jquery? Use of queue() in jquery?

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jQuery Interview Questions and Answers for Experienced

35) How do you disable jQuery animation?

You need to use the jQuery property “jQuery.fx.off” and change the settings to true for disabling jQuery animation.

36) Is jQuery a JSON library or JavaScript file?

jQuery is said to be a feature-rich library of single JavaScript files which consists of DOM/CSS manipulations, AJAX functions, event effects or animations, and various commonly used plugins.

37) What are events in jQuery?

Actions taken by users on a webpage are called events and handling responses is called event handling. jQuery provides easy methods for attaching event handlers to selected elements. So, when any event occurs, the provided function is executed.

38) What is the use of jQuery.length method?

jQuery.length method is used to count the number of the elements of the jQuery object.

39) What is a jQuery click event?

jQuery click event happens when we click on an HTML element. jQuery gives a function of click() method which allows the click event to start.

For example, $(“p”).click() will start the click event on a browser page whenever the elements with paragraph tag are clicked.

Syntax:

$(selector).click(function(){

//code that runs when the click event is triggered

});

40. How to perform jQuery AJAX requests?

jQuery uses the ajax() method to perform an AJAX (asynchronous HTTP) request.

Syntax: $.ajax({name:value, name:value, … }).

URL: A URL is provided to send the request to. Default is the current page.
success(result,status,xhr): success callback function runs when the request is successful.
error(xhr,status,error): When a request fails error function is used to run.
async: It is a boolean value which tells that whether the request is handled asynchronously or not.
complete(xhr,status) : when a request is completed (after success and error functions are handled) this function used to run
xhr : To create a XMLHttpRequest object this function is used.

41. What does the following code do?

$( “div#firstDiv, div.firstDiv, ol#items > [name$='firstDiv’]” )

The code tells of getting elements that fulfill multiple selectors at once. This code returns a jQuery object having the results of the query.

This code makes a query to retrieve those
elements by using the id value firstDiv with all
elements which have the class value firstDiv and all those elements that are children of the

42. What does the following code do?

$( “div” ).css( “width”, “500px” )

.add( “p” )

.css( “background-color”, “yellow” );

Firstly it selects all the

elements and make the width of 500px and adds all the

elements to the selection after which the background color is changed to yellow for all the

and

elements. It is an example of method chaining in jQuery which was meant to achieve multiple things in single instruction.

43. Tell difference between jQuery.get() method and jQuery.ajax() method?

jQuery.ajax() allows the making of highly-customized AJAX requests, with different options like, how long to wait for a response, what next to be done after the request is successful, how to manage a failure scenario, the request needed to be sent is blocking (synchronous) or non-blocking (asynchronous), what format to be fixed as the response, and many more options to customize these things.

jQuery.get() use jQuery.ajax() underneath to make an AJAX request to get simple retrieval of information.

Some of the pre-built AJAX requests are:
- jQuery.post() for creating a post requests
- jQuery.getScript() to load a JavaScript file and then process it from the server using this request.
- jQuery.getJSON() to load JSON-encoded data by using a GET HTTP request from the server

44. In the following given codes which is more efficient and why? document.getElementById(“jobinterviewninjas”); OR $("#jobinterviewninjas”);

The code document.getElementById( “jobinterviewninjas”); is more efficient because its the pure JavaScript version.
To make DOM manipulation easier, jQuery is built on top of JavaScript. We must remember that jQuery is not always better than pure JavaScript and is used only to add advantages to our project.

45. Write a jQuery code selector which will query all elements whose ID ends with the string “IB”?

We can use the following selector: $("[id$='IB’]")

46. Explain the .promise() jQuery function.

When all actions of a certain type are bound to the collection, queued have been resolved and ended by using the .promise() method which returns a dynamically generated promise.

The method takes two optional arguments:

type - The default type is “fx” which tells that all animations of the selected elements are completed and returned promise is resolved.
target - If a target object is specified, .promise() will attach to promise to that specified object and then return it rather than creating a new one.

47. How between prop() and attr()s are different?

Both prop() and attr() is used to set the value of the specified property of an element attribute. Whereas the attr() gives the default value whereas prop() returns its current value of a property

48. What is JQuery.noConflict?

jQuery no-conflict is an option in jQuery to overcome the conflicts between the different js frameworks or libraries. When we use jQuery no-conflict mode the we replace the $ to a new variable and assign to jQuery and some other JavaScript libraries. Also, use the $ as a function or variable that jQuery has.

49. What is JQuery UI?

jQuery UI enables the applications to have a cool user interface and animation in a faster way. It uses a set of plugins that include interface interactions, effects, animations, widgets, and themes built on the JavaScript Library. Cohesive and consistent APIs is created by using jQuery and also extend jQuery prototype objects. With that prototype object, you can enable all jQuery objects to inherit any method that you add.

Interactions

We can use interactions for basic mouse-based behaviors to any element. Examples of Interactions are the following:

Draggable
Droppable
Resizable
Selectable
Sortable

50. How to handle Controls attribute Using jQuery?

For handle Controls attribute we use .addClass(), .removeClass(), .css(), .toggleClass(), etc jQuery to manage all css and html attributes of any html control.

51: What is chaining in jQuery?

It is a strong feature of jQuery. It means identifying multiple functions and/or selectors to an element. Chaining also reduces the code segment and keeps it tidy and easily understandable. It is used to make jQuery built-in functions which make the compilation faster.

By using chaining you can write code as follows:

$(document).ready(function() {

$("#div2”).html($("#txtBox”).prop(“readonly”)) + ‘
’;

$("#div3”).html($("#txtBox”).attr(“readonly”));

});

52: How parent(), children() and siblings() methods works in jQuery?

The parent() function brings back the parent of the selected or matched element whereas children() and siblings() function returns all the children & siblings of given HTML elements.

53: Explain bind() elements and unbind elements in jQuery?

The jQuery bind() function attaches an event handler to elements, whereas the unbind() does the opposite and detaches an existing event handler from elements. You can use basic HTML code to make the HTML elements.

54: How to remove a DOM element using jQuery?

Sometimes we do require to delete all child nodes and remove DOM elements using jQuery to make a web page dynamic. There are some of the jQuery which can be used to remove DOM elements. Here are the options:

empty()
remove()
html()

55. What is the use of a jQuery filter?

There are various types of filters that JQuery supports, such as:

.eq()
.first()
.last()
.filter()
.has()
.not()

56. What is the use of jQuery.ajax method()?

The ajax() method is to make an AJAX (asynchronous HTTP) request. It provides control over data sending and response data. It allows the error handling that happens during a call and the data if the call to the ajax page is successful.

Some basic parameters are required for jQuery.ajax Method is:

type: (GET or POST) are the type of requests to make.
url: It specifies the URL to send the request to. The current page is set by default.
contentType: The content type used when sending data to the server. The default is “application/x-www-form-urlencoded".
dataType: The data type expected of the server response.
data: Specifies data to be sent to the server.
success(result,status,xhr): A function to run when the request is successfully completed.
error(xhr,status,error): A function to run when the request fails.

57. What is an attribute in jQuery?

There are quite important properties of DOM or HTML elements that are used in jQuery such as for the tag the src, class, id, title, and other essential properties. jQuery provides different ways to manipulate an element’s attribute and provides us access to the element which assists us in changing its properties.

attr( properties ) - This attribute sets a key/value object as properties to all selected or matched elements.
attr( key, fn ) - It sets a single property to a calculated value, on all selected elements.
removeAttr( name ) - Remove an attribute from each selected element.
hasClass( class ) - Returns true if the specific class is present on at least one of the set of matched elements.
removeClass( class ) - Removes all/specified class(es) from the set of selected elements.
toggleClass( class ) - Adds the specified class if not already present and vice versa.
html( ) - Gets the HTML contents (innerHTML) of the first selected element.
html( val ) - Sets the HTML contents of all matched element.
text( ) - Gets the combined text contents of each of the matched elements.
text( val ) - Sets the text contents of all matched or selected elements.
val( ) - Gets the first matched element’s input value.

58. What are jQuery Events?

At the time of designing a dynamic web page, it is essential to add some events such as Mouse Click, for forms submit the form after a button click, change color after a click, etc. We generally use some event handlers to perform the action in almost all the web pages. Some of them are bind(), unbind(), blur(), off(), hover(), on(), one(), ready(), trigger() etc.

59. How are you able to find browser and browser versions in jQuery?

Using $.browser property of jQuery takes you to the browser information.

Note: $.browser is not recommended to use by jQuery itself, and because of this function has been migrated to jQuery.migrate plugin which needs to be downloaded first if the user wants to use it. Please note that, use this only when highly required. It is better and recommended to not use browser-specific codes

60: Tell us the difference between Map and Grep function in jQuery?

In $.map() you generally need to loop over each element in an array and change its value whilst, whereas the $. Grep() function will return the filtered array by using filter condition from a present array.

61: What are jQuery plugins?

Plugins are basically a piece of collective code. jQuery plugins are the codes written in a standard JavaScript file that provide useful jQuery methods which can be used along with jQuery library methods.

You need to add the method you use in plugins that must contain a semicolon (;) at the last. This method will return to an object (jQuery) unless mentioned. Use each to iterate over the current set of matched elements. It produces light and compatible code as per the requirement. Always attach the plugin to jQuery directly at the place of using $, so you can use a custom alias via the noConflict() method (via the jQuery Team).

62: What is jQuery.holdReady() function?

jQuery.holdReady() function tells that it will hold or release the execution of jQuery’s ready event. This method will be called before we run the ready event. To delay the ready event, we need to hold it and need to call jQuery.holdReady(true), and when it’s time to release the event we need to call jQuery.holdReady(false). This function is used when we want to load the jQuery plugin of the ready event or want to perform certain events/functions before the document.ready() loads.

63: What is resize() function in jQuery?

This method in jQuery is used for resizing or changing the size of the element. You need to use .resize() function for this in jQuery.

64: Tell the use of Draggable, Droppable, Resizable, Selectable in jQuery UI?

For interaction sections there are only 5 plugins available; that is Draggable, Droppable, Resizable, Selectable, and Sortable. These plugins handle complex behaviors such as drag and drop, resizing, selection and sorting.

Graphical representation of jQuery UI subordinates:

Draggable: It allows drag functionality on DOM elements. You need to click the object with the mouse and drag it anywhere within the viewport.

Droppable: It allows any DOM element to be dropped, it is related to drag elements that need to be dropped somewhere.

Resizable: It allows DOM elements to be resizable. Wit is used to get the desired width or height.

Selectable: It allows a DOM element (or group of elements) to be selectable. Draw a box and grab it with your mouse cursor to select items.

Sortable: It allows a group of DOM elements to be sortable. Sortable items share dragging properties.

65: Tell us the history & uses of jQuery UI?

jQuery UI is really easy to learn and it gives abstractions for low-level interaction and animation to advanced effects and high-level interface, theme-based widgets which are built on top of the jQuery JavaScript Library which is used to build highly interactive web applications. It is categorized into four groups that are core, interactions, widgets, and effects.

The components of jQuery UI are:
Core: It’s a base for other widgets and effects where they can work properly.
Interactions: It handles interaction behavior like Drag, Drop, Sort, etc.
Widgets: This UI controls tabs, dialog, slider, etc.
Effects: There are some ready-to-use effects like clip, bounce, explode, etc.

66: Define jQuery UI Autocomplete?

jQuery UI Autocomplete is one of the best widgets ON websites that are used by each and every website. It does require some functional CSS otherwise it won’t work. If you make a custom theme then use a widget’s specific CSS as a starting point. This widget manipulates its element’s value programmatically, therefore a native change event may not be fired when the element’s value changes.

We can make jQuery UI autocomplete, using AJAX, to build a list (server-side) and then bind that list into a text box using JavaScript. However, there are other ways to make autocomplete. The most robust, efficient, and free tool of autocomplete is jQuery UI autocomplete and there is no need to license it.

67: What do you understand by jQuery UI Sortable and how to use it?

The jQuery UI is a library file provided by jQuery for having an enhanced user interface. Using sortable action we can reorder the DOM elements in the defined area. Users have to click on the object and drag that item to a new place and the other items will be automatically arranged. You can see the given examples.

Include the jQuery js file.

Include the jQuery UI js file.

68: Why use jQuery $ sign?

The basic and major operation in jQuery is selecting an element in DOM. It can be done by using $() construct adding a string parameter that contains CSS selector expression. $() will also return to zero or more DOM elements on which it is required to apply an effect or a style.

69: What is the slice() method in jQuery?

This method selects a subsection of the matched elements by giving a range of indices. In simple words, it gives the set of DOM elements on the basis of parameters are given (start, end).

**Syntax: .**slice(start, end[Optional])

Start: It is the first and mandatory parameter for using the slice method. It identifies from where you are selecting the elements.

End: This is a non-mandatory parameter that specifies the range or ending point of the selection.

Note: The Negative Indices started from -1. This last element is denoted by index -1 and so on.

70: What is queue() in Jquery? Use of queue() in jquery?

It is a custom effect category in jQuery. Its sole purpose is to delay the execution of subsequent items in the execution queue.

delay( duration [, queueName ] )

queueName is a name of the queue which needs to be delayed and delay time is to be inserted. By default, it is an “fx” queue. An “fx” queue is also known as an effects queue.

These interview questions are enough to clear the technical interview related to the jQuery section but prepare well. Basically in an interview, there are a total of 2-5 questions that are asked related to jQuery if it is not fully focused on jQuery.

You need to well prepare these jquery interview questions and answers to crack your interview questions related to the jQuery topic. In the above questions, we have tried to cover basic jquery questions, technical jquery questions, and coding jquery questions with examples to freshers and professionals. If you have any questions or need help related to interview questions and answers on jquery then feel free to reach us.

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