One of the most popular libraries of JavaScript is jQuery. It is a tiny library for web development that provides an exciting web experience. In this article, we have collected a set of frequently asked jQuery interview questions to get you familiar with the interview's topics. If you are looking to learn JavaScript, read about its learning path here.
What is JQuery?
JQuery is a fast, small, and feature-rich JavaScript library. It simplifies things like HTML document traversal and manipulation, event handling, and animation with an easy-to-use API that works across many browsers. With versatility and extensibility, jQuery has changed how millions of people write JavaScript.
What is JQuery Used For?
jQuery is mainly used for DOM (Document Object Model) manipulation, which allows you to modify a web page's structure, style, and content. Some of the common things that jQuery is used for include:
- Selecting and manipulating HTML elements
- Traversing and modifying the DOM tree
- Handling events such as clicks, mouseover, and keypress
- Creating animations and effects such as fading, sliding, and hiding elements
- Making AJAX requests to retrieve data from a server without reloading the page
- Creating plugins to extend the functionality of jQuery
Because of its ease of use, jQuery has become one of the most popular JavaScript libraries and is widely used in developing web applications and websites.
Basic JQuery Interview Questions
Here are some basic jquery interview questions:
1. Why is jQuery known as a feature-rich library?
This is because jQuery has several features such as easy DOM manipulation, event handling, built-in animations, cross-browser compatibility, supports CSS3, and is lightweight.
2. In what scenarios jQuery can be used?
jQuery is used mainly to add animation effects, call functions on events, apply dynamic or static CSS, and manipulate purposes.
3. Can you select all elements using jQuery? How?
Yes, all elements can be selected using jQuery using $('*') available in a DOM.
4. What are different selectors in jQuery used for?
There following selectors in jQuery is used as:
$('div') is used for selection all div tags in the document, $('#TextId') is used for selecting elements whose ID is TextId and $('.myclass') is used for selecting all elements whose class is .myclass.
5. What is the purpose of jQuery AJAX?
AJAX stands for Asynchronous JavaScript and XML. It helps in loading and exchanging data without a browser page refresh and only via server. jQuery provides a rich set of AJAX methods to develop web applications.
6. How to deal with cookies in jQuery?
Dough cookie plugin can be used to deal with cookies in jQuery. It has powerful features and is easy to use. For example: $.dough(“cookie_name”, “cookie_value”);
can be used to create a cookie.
7. Popularly asked jQuery interview questions are how to get the text contents and set the text contents of an element using jQuery?
Text () method is used to get combined text contents of all matched elements, and text(Val) is used to set those text contents.
8. How is css(‘width’) different from width() in jQuery?
These two are different methods available in jQuery to change the width of an element. The difference is that in CSS('width'), we have to add px in the width value while this is not required in width().
9. Does Bootstrap require jQuery?
jQuery is used for JavaScript plugins by Bootstrap. However, if we use the CSS part of Bootstrap, jQuery is not needed.
10. How can you include jQuery on a page?
jQuery can be included in a page inside the script tag, remote copy of Ajax API and jQuery.com, embedder script using client script object and a local copy of script manager control.
11. What are the advantages of jQuery?
- jQuery is easy to use and understand, even for people with limited programming experience.
- It simplifies common JavaScript tasks, such as traversing the Document Object Model (DOM), handling events, and creating animations.
- jQuery is cross-browser compatible, which works well in most major web browsers.
12. How is jQuery different from other javascript frameworks?
jQuery is a JavaScript library, while other JavaScript frameworks, such as AngularJS and React, are JavaScript frameworks. The main difference between the two is that a library is a collection of pre-written code that you can use to perform specific tasks, while a framework is a structure in which you build your code on top.
13. List some features of jQuery.
- DOM manipulation and traversal
- Event handling
- Effects and animations
- AJAX support
- Cross-browser compatibility
- Support for plugins and extensions
14. Is jQuery a JavaScript or JSON library file?
jQuery is a JavaScript library file.
15. Does jQuery work for both HTML and XML documents?
Yes, jQuery can work with both HTML and XML documents.
16. What is jQuery Mobile?
jQuery Mobile is a JavaScript framework that allows you to create mobile web applications with a consistent look and feel across different platforms and devices. It is based on the jQuery library and provides a set of UI widgets and tools for building mobile-friendly web pages and applications.
17. What is the $() function in the jQuery library?
The $() function is an alias for the jQuery() function. It is used to select elements from the DOM and perform various operations.
18. Explain $(document).ready() function?
This function is used to ensure that the DOM is fully loaded before any jQuery code is executed. This function takes a function as an argument, and the function passed to it will be executed when the DOM is ready. This is useful for ensuring that elements on the page are available before interacting with them.
19. What is the exact difference between the methods onload() and document? ready()?
The onload() method is JavaScript when the page finishes loading. The document. a Ready () method is a jQuery method called when the DOM is ready. The main difference is that onload() waits for all assets on the page to be loaded, including images and other external resources, during the document. Ready () only remains for the DOM to be prepared.
20. Describe jQuery Connect in brief. Also, list its uses.
jQuery Connect is a plugin for jQuery that allows you to connect to other web pages and services using AJAX. It can be used to retrieve data from other websites, for example, to display information from another site on your site or to post data to another place.
21. What are the jQuery functions used to provide effects?
jQuery provides several functions for creating effects, such as hide(), show(), slideUp(), slideDown(), fadeIn(), and fadeOut(). These functions can create animations and visual effects on elements in the DOM.
22. What is the use of the CSS () method in jQuery?
The CSS () method in jQuery is used to retrieve or set the value of a CSS property for the selected elements.
23. Which jquery method is used to hide selected elements?
The hide() method in jQuery is used to hide selected elements.
24. What are events in jQuery?
Events in jQuery are actions or occurrences in the browser, such as a user clicking a button or hovering over an element.
25. How to iterate/loop through all p elements in jquery.
To iterate/loop through all p elements in jQuery, you can use the each() method like so:
var paragraphs = $("p"); for(var i = 0; i < paragraphs.length; i++) { var p = paragraphs[i]; // code to be executed }
26. What is the significance of jQuery.length?
jQuery.length is a property that returns the number of elements in the selected jQuery object.
27. What is jQuery click event?
The click event in jQuery is triggered when a user clicks on an element. It can perform a specific action when an element is clicked.
28. What is the purpose of JQuery's delay() method? Can you use this for different types of browsers like (Internet Explorer)?
The delay() method in jQuery is used to delay the execution of an animation or a function for a specified time. It can be used in different types of browsers, including Internet Explorer.
29. Can you explain about ajaxStart() functions?
The ajaxStart() function in jQuery is a method triggered when an AJAX request is sent. It can perform a specific action when an AJAX request is sent, such as displaying a loading message.
30. Can you explain the ajaxComplete() function?
The ajaxComplete() function in jQuery is a method that is triggered when an AJAX request is completed. It can perform a specific action when an AJAX request is completed, such as hiding a loading message.
31. Can you say something about jQuery each() method?
Each () method in jQuery is used to iterate through a set of elements and perform a specific action on each element. It can loop through a set of elements and perform a specific action on each element.
32. What is the difference between javascript and jquery?
JavaScript is a programming language that can add interactivity and other dynamic features to websites. jQuery is a library built on top of JavaScript that makes it easier to work with the Document Object Model (DOM) and perform common tasks such as event handling and animation.
33. What is the difference between the $(window).load and $(document)? Ready functions in jQuery?
The $(window).load function is triggered when all assets, including images, have finished loading on the page. The $(document).ready function is activated when the DOM (Document Object Model) is fully loaded and ready for manipulation. The $(document).ready function is generally used to initialize scripts, while the $(window).
34. What exactly is a jQuery Data Table plugin? Also, explain the uses with examples.
A jQuery Data Table plugin is a tool that allows for easy manipulation and organization of data in a table format. This can include sorting, searching, pagination, and other features. For example, a website displaying a large amount of data in a table format could use a jQuery Data Table plugin to allow users to sort and search through the data easily.
35. What is the purpose of JQuery's serialize() method?
The jQuery serialize() method converts form data into a string format that can be easily sent to a server via an AJAX request.
36. Explain how CSS classes can be manipulated in HTML using jQuery.
jQuery allows for the manipulation of CSS classes in HTML through the use of the addClass(), removeClass(), and toggleClass() methods. The addClass() method is used to add a CSS class to an HTML element, while the removeClass() method is used to remove a CSS class from an HTML element.
37. State some different types of jQuery methods.
Some different types of jQuery methods include:
- Event methods: such as click(), hover(), and focus()
- Traversing methods: such as children(), parent(), and siblings()
- DOM manipulation methods: such as append(), prepend(), and replaceWith()
- CSS manipulation methods: such as addClass(), removeClass(), and CSS()
- Animation methods: such as animate(), fadeIn(), and slideUp().
Advanced JQuery Interview Questions
Next up, let us have a look at advanced jquery interview questions!
38. Why are Ajax methods preferred in jQuery?
jQuery Ajax methods are simple, offer cross-browser support, send GET and POST requests and load XML, JSON, Scripts or HTML.
39. How is parent() method in jQuery different from parents() method?
The parent() function travels only a single level in the DOM tree, whereas parents() searches through the entire DOM tree.
40. What is jquery.min.js?
It is a compressed version of jquery.js as shorter variable names are used to preserve bandwidth. It functions precisely similar to jquery.js. The compressed version is used to increase the efficiency of web pages.
41. What is a content distribution network?
A content distribution network or CDN is an extensive distributed system of servers deployed across the Internet. Its primary objective is to offer highly available as well as high-performance content to end-users.
42. Ajax functions are generally asked as a part of jQuery interview questions. List some of them.
- .ajaxStop()- when all requests are complete, this registers the handler to be called.
- .ajaxStart()- when the first Ajax request begins, this registers the handler to be called.
- .ajaxSuccess()- when an ajax request is completed, this registers the handler to be called.
43. If you want to check if an element is empty or not, which methods can be used?
We can use the '.empt' selector or '$.trim()' function to check if an element is empty.
44. How is 'this' different from '$(this)' in jQuery?
We use $(this) to use jQuery methods, which refers to the DOM element.
45. What is a prop() in jQuery? How is it different from Attr()?
The prop() method is used to obtain the value of the first element property, and Attr() is used to extract the value of the first element's attribute.
46. What is the advantage of method chaining in jQuery?
Multiple jQuery commands on a particular element can be executed in one go with chaining. It helps in implementing various actions on an element rather than one after the other.
47. Tell something about the finish method in jQuery.
The .finish() method stops all queued animations and place all the elements in their final state.
48. Explain the operation of the jQuery connect() method.
The jQuery connect() method creates a connection to a remote server using the WebSockets protocol. It allows for real-time communication between the client and server, enabling the ability to push data from the server to the client in real-time.
49. Distinguish between jquery.min.js and jquery.js.
jquery.min.js is a minified version of the jQuery library, which has been compressed to reduce its file size.
50. Explain the benefits of using a CDN for the jQuery files.
Using a Content Delivery Network (CDN) for the jQuery files can provide several benefits, such as faster load times for users, as the files are served from a location closer to the user's location.
51. Can you describe the various methods for extracting a query text using regular expressions?
There are several methods for extracting a query text using regular expressions, such as using the match() or exec() methods to search for a specific pattern in a string or using the search() method to find the index of the first occurrence of a particular pattern in a string.
52. Explain the use of the event.preventDefault() method.
The event.preventDefault() method is used to prevent the default action of an event from occurring.
53. What are the benefits of Using jQquery instead of javascript in an ASP.NET web application?
Some benefits of using jQuery instead of JavaScript in an ASP.NET web application include built-in cross-browser compatibility support, a large library of pre-built functions, and a simpler and more consistent syntax.
54. What is event.stopPropagation()?
The event.stopPropagation() method stops an event from propagating to parent elements.
55. Is it possible to pause or postpone the execution of the document.ready for a period of time?
Yes, it is possible to pause or postpone the execution of the document—ready event for a period of time by using the setTimeout() function. The setTimeout() function takes two arguments: a function to execute and a time delay in milliseconds.
You can also use the setTimeout() function to wrap the entire document. Ready event to delay its execution.
For example:
56. Would you still favor jQuery in a case when things can be done simply using javascript?
Whether to favor jQuery or JavaScript depends on the developer's specific use case and skillset. jQuery can simplify complex tasks and provide cross-browser compatibility, but in some cases, it may be simpler and more efficient to use plain JavaScript.
JQuery Coding Questions
57. How to perform jQuery AJAX requests?
jQuery provides several methods for performing AJAX requests, the most commonly used one being the $.ajax() method. This method allows you to send HTTP requests to a server and handle the response without having to refresh the entire page.
Here's an example of how to use the $.ajax() method to make a GET request to a server:
58. What does the following code do?
$( "div#firstDiv, div.firstDiv, ol#items > [name$='firstDiv']" )
The code is a jQuery selector that selects multiple elements from the DOM (Document Object Model).
The code selects
- the first div element with an id of "firstDiv"
- all div elements with a class of "firstDiv"
- all elements with a name attribute that ends with "firstDiv" and are children of an ol element with an id of "items".
59. Write a jQuery code to create and delete cookies from the browser.
Here is an example of how to create a cookie using jQuery:
To delete a cookie, you can set its expiration date to a past date:
60. Can you explain the difference between jQuery.get() and jQuery.ajax()?
Both methods allow you to send an HTTP request to a server and handle the response, but they have some key differences:
- $.get() is a shorthand method for performing a GET request using $.ajax(). It is a simpler method and is used for quick and simple requests, such as retrieving data from a server. The basic syntax for $.get() is $.get(url, data, callback).
- $.ajax() is a more powerful and flexible method for performing AJAX requests. It can be used to perform any type of HTTP request (GET, POST, PUT, etc.). Here's an example of how to use $.get() and $.ajax() to make a GET request to a server:
61. Write a code snippet for preventing the default behavior of the submit button for performing another event.
Code snippet that demonstrates how to prevent the default behavior of a submit button and perform another event using jQuery:
It's also possible to prevent the default behavior of the submit button by returning false from the submit event handler:
62. Which of the two lines of code below is more efficient and why?
document.getElementById("interviewBit"); OR $("#interviewBit");
The first line of code uses the native JavaScript method document.getElementById(), which is considered to be more efficient than the jQuery method $() because it is a native JavaScript method and it doesn't have to go through the additional layers of abstraction that jQuery uses.
The second line of code uses the jQuery method $() which is a shorthand for jQuery(). The $() function is a wrapper for the jQuery() function, which is used to perform DOM manipulation, event handling, and animation. jQuery uses document.getElementById() internally to get the element, but it also adds the overhead of the jQuery library and its additional layers of abstraction.
63. How do you disable elements in Jquery Using "attr"?
To disable an element using jQuery's attr() method, you can set the "disabled" attribute to "true" on the element. Here's an example of how to disable a button element with the ID "myButton":
64. Can you write a jQuery code selector that needs to be used for querying all elements whose ID ends with string “IB”?
The jQuery code selector that can be used to query all elements whose ID ends with string “IB” is: $("[id$='IB']")
This selector selects all elements that have an ID attribute that ends with "IB".
65. Explain the .promise() method in jQuery.
The .promise() method in jQuery is used to return a promise that is resolved when all of the elements in the set have completed a specific action. For example, when all animations on the set of elements have completed. The returned promise object can be used to attach callbacks that will be executed when the promise is fulfilled or rejected.
66. Write a jQquery code snippet to sort a string array?
Here's an example of how to sort a string array using jQuery:
67. Can you provide an example of chaining using a code snippet?
Chaining is a technique in jQuery that allows you to perform multiple actions on a set of elements using a single line of code. Here's an example of how to use chaining to fade out an element, change its text, and then fade it back in:
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Conclusion
With this, we come to the end of jquery Interview questions. jQuery finds its application in web development, and if you are looking to make a career in it, you must enroll in Simplilearn’s Full-stack web developer course. Get certified and make your profile stand out in the coming jquery interviews! Start now!