JQuery Interview Questions For Freshers & Experienced

  • Question 1) What is JQuery?
  • Question 2) Enlist few advantages of using Jquery?
  • Question 3) What are the core features of jQuery?
  • Question 4) What is the difference between JavaScript and jQuery?
  • Question 5) What are the different type of selectors in Jquery?
  • Question 6) What is $() in jQuery?
  • Question 7) What is jQuery Ajax?
  • Question 8) Explain width() vs css('width') in JQuery?
  • Question 9) What is the use of param() method in JQuery?
  • Question 10) Explain bind() vs live() vs delegate() methods in Jquery?
  • Question 11) What are the various ajax functions available in Jquery ?
  • Question 12) What is difference between $(this) and this in jQuery?
  • Question 13) Please explain .empty() vs .remove() vs .detach() in Jquery?
  • Sharad Jaiswal
  • 11th Dec, 2019
  • 1030 Followers

jQuery:

jQuery is a fast, lightweight and concise JavaScript library that supports all browsers. It is easy to play with DOM, event handlings, animations, and AJAX interactions for fast web development with jQuery. Its slogan "minimal lines of code" helping the developers to write a few lines of code to do the most things. Moreover, jQuery is active and "rival" cooperation. It seems to be in the overall development of JavaScript, not just to one's private ends.

JQuery Interview Questions
Updated ON

11th Dec, 2019

No. of Questions

35

Posted In

JavaScript

Author

Sharad Jaiswal

Key Features of Jquery

Below are few major features of Jquery

Easy DOM manipulation

Support AJAX

JSON parsing

Extensibile through plug-ins

Cross-browser support

Easy Integration

Lightweight

Event handling & Animation

Protection Against XSS Attacks

JQuery Interview Questions

Q1. What is JQuery?

JQuery is the most popular JavaScript library due to it’s lightweight and extendable functionality used for creating efficient websites. It provides an easy method for HTML DOM traversing and manipulation and client-side animations. The purpose of jQuery is to make the code simple, short and readable.

For using jQuery one should have prior knowledge of HTML, CSS, and JavaScript.

Q2. Enlist few advantages of using Jquery?

Advantages of using jQuery:

  • Create Responsive websites using AJAX
  • Allows creation of dynamic web pages and web applications
  • Extendable
  • Manages cross-browser issues
  • Light-weight entity
  • DOM Manipulation
  • Fast
  • Implementing complex functionalities by writing lesser lines of code
  • Easy and readable code
  • No overhead in learning a new syntax
  • Avoids common browser errors

Q3. What are the core features of jQuery?

jQuery library contains the following features:

  • HTML/DOM manipulation
  • Develop AJAX Applications
  • Event Handling
  • Create Animations and Effects
  • Utilities
  • Create own plugins
  • Select DOM Elements
  • Cross-browser support

Q4. What is the difference between JavaScript and jQuery?

  • JavaScript is a programming language. jQuery is a javascript library.
  • One should know JavaScript prior to using jQuery.
  • In JavaScript, you need to write a long code. Whereas jQuery can perform the same function in very fewer lines of code.
  • JavaScript is faster for accessing DOM. jQuery is slower.
  • Developers are prone to make browser-related errors in JavaScript. Whereas jQuery developers don’t have to worry about browser compatibility issues.

Q5. What are the different type of selectors in Jquery?

jQuery selectors help you to select and manipulate HTML Elements. They are :

  • Basic jQuery Selectors
  • Content jQuery Selectors
  • Hierarchy jQuery Selectors
  • Selectors based on Index
  • Visibility Selectors
  • Child Selectors Attribute Selectors
  • Content Selectors
  • Form Selectors

Q6. What is $() in jQuery?

$() in jQuery a syntax in jQuery which is used to select the Html elements or collection matching elements from DOM.

Example,

$(‘#id’) for selecting element by id
$(‘.classname’) for selecting element by class

Q7. What is jQuery Ajax?

AJAX stands for (Asynchronous JavaScript and XML). It is a process of exchanging data with a server and refreshing the whole page and updating applied changes without reloading the whole page.

jQuery ajax() method helps to send asynchronous HTTP requests to the server.

Q8. Explain width() vs css('width') in JQuery?

JQuery has two ways to set the width of an element. You can set either using CSS or jQuery methods. The main difference is in datatype. In the CSS method, you need to append 'px' to the width value and with "width" you don’t need to specify. CSS method returns string value while width returns an integer value.

For manipulation purposes, the width function is the best option.

Q9. What is the use of param() method in JQuery?

Param() method in jquery creates a serialized representation of an array or an object from element values. The object stands for an array or a plain object or an object to serialize. Traditional has type Boolean indicating to perform a traditional "shallow" serialization.

Syntax :

$.param(object,trad)

Q10. Explain bind() vs live() vs delegate() methods in Jquery?

.bind() attaches events to elements that exist or match the selector at the time the call is made i.e will only apply to the items you currently have selected in your jQuery object.

.live() works for existing and future matching elements i.e will apply to all current matching elements, as well as any you might add in the future.

.delegate() method adds one or more event handlers to the specified element.

Q11. What are the various ajax functions available in Jquery ?

The list of methods are :

  • $.ajax()
  • $.ajaxPrefilter
  • $.ajaxSetup
  • $.get()
  • $.getJSON()
  • $.parseJSON()
  • $.post()
  • ajaxSend()
  • ajaxStart()
  • ajaxStop()
  • ajaxSuccess()
  • load()
  • serialize()
  • serializeArray()

Q12. What is difference between $(this) and this in jQuery?

$(this) and this refers to the same element. The main difference is in the way they are used. While using this, you can call the DOM method but not jQuery methods.

Whereas, while using $(this), you can call jQuery methods on it, but not DOM methods.

Q13. Please explain .empty() vs .remove() vs .detach() in Jquery?

empty() – This method removes all content and child elements from the selected element and does not remove the selected elements.

remove() – This method removes all child elements with selected elements and also you can restore all data but not event handlers of removed elements from the DOM. All data and events related to elements will be removed.

detach() – This method removes all child elements with selected elements. Even though it keeps all data and event handlers of the removed elements it is preferred to remove elements but it keeps a copy of the removed elements which can be reused later.

Q14. List some effects methods used in jQuery?

Some of the methods used in jQuery to provide effects are :

  • Animate() - Used to customize animations on any selected elements.
  • Clearqueue() – Used to remove any remaining queued functions from the selected elements.
  • Delay() – to set a delay for all queued functions of the selected elements.
  • Fadein() – fades in the selected elements.
  • Fadeout() – fades out the selected elements.
  • Fadeto() – to fade in/out the selected elements to a required opacity.
  • Dequeue() – to execute the functions after removing the next function from the queue.
  • Fadetoggle() – to toggle between fadeout() and fadein() methods.
  • Finish() – to stop, remove and complete any/all queued animations for the selected elements.

Q15. What is the use of toggle() method in JQuery?

The jQuery toggle() is a type of method which is used to toggle between two or more functions such as hide() & show() method

  • Show() is used to show the hidden elements.
  • Hide() is used to hide the visible elements.

Q16. What is the use of css() method in JQuery?

Css() method in jQuery is used to set or return style properties of one or more style for the selected elements. It is an easy way to get the computed style properties for the elements in the set of matched elements.

Q17. What is jQuery connect?

jQuery is a plugin that is used to connect or bind a function to another function. It is more of assigning a handler for another function. It is used to execute a function when a function from another plugin is executed.

Q18. What is a CDN?

CDN stands for a (Content Delivery Network). It is a system of computers with scripts and other content on them that are widely used by many web pages. It can be a very effective way to speed up a web page

Q19. What is a use of jQuery filter?

The jQuery filter() method returns elements that match a certain criterion. The filter () method can construct a new jQuery object from a subset of the matching elements. The required criteria are matched against each element. Elements that do not match the supplied criteria are removed from the selection and those that match are returned.

Q20. What is ID and class selector in jQuery?

The ID and class selector in jQuery helps to find and select DOM elements easily. The class selector is used in case we need to select multiple elements, which have the same CSS class. Searching and finding HTML elements using selectors are natural and very easy.

Q21. What is use of use of serialize() method in JQuery?

Serialize() method serializes a set of input elements into a string of data. It creates a URL encoded text string by serializing form values. The serialized values can be used in the URL query string while making an AJAX request.

Syntax : 
$(selector).serialize()

Q22. How to stop event propogation in Jquery?

Event.stopPropogation() is used for stopping event propagation. It prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event. You can use the event.isPropagationStopped() method to check whether this method was called for the event.

Syntax : 
event.stopPropagation()

Q23. What is use of the animate() method in jQuery?

The animate() method performs custom animation of a set of CSS properties. This method changes an element from one state to another with CSS styles. The CSS property value is changed gradually to create an animated effect.

Syntax : 
(selector).animate({styles},speed,easing,callback)

The speed parameter specifies the duration of the effect.

The callback parameter is a function to be executed after the animation completes.

Q24. How to read, write and delete cookies in jQuery?

In jQuery, reading, writing and deleting cookies are done by using dough cookie plugin.

The syntax for reading cookie :

$.dough(“cookie_name”);

The syntax for writing cookie :

$.dough(“cookie_name”,”cookie_value”);

The syntax for deleting cookies :

$.dough(“cookie_name”,”remove”)

Q25. What is jQuery UI?

jQuery UI is a set of user interface interactions, effects, widgets, and themes built on top of the jQuery JavaScript Library. jQuery UI is the perfect choice for building highly interactive web applications and to add a date picker to a form of control.

It contains many widgets that maintain state and therefore have a slightly different usage pattern than typical jQuery plugins. All of jQuery UI's widgets use the same patterns, so if you learn how to use one, then you'll know how to use all of them.

Q26. What is use of slice() method in jQuery?

The slice() method reduces the set of matched elements to a subset specified by a range of indices.

Syntax : 
.slice(start[,end])

A start has a type integer indicating the 0-based position at which the elements begin to be selected. If negative, it indicates an offset from the end of the set.

The end has a type integer indicating the 0-based position at which the elements stop being selected. If negative, it indicates an offset from the end of the set.

Q27. How to select all elements in jQuery?

Different selectors can be used to select the required element or even a class of elements.

jQuery selectors allow a user to select and manipulate HTML element(s).

The selection or finding of HTML elements can be based on their name, id, classes, type, attributes, values of attributes and many others.

All selectors in jQuery start with a $() dollar sign.

For example, User can select all elements on a page as following: $("a")

Q28. How to set and get the value of an element using jQuery?

To set any form value of an element using jQuery val() function is to be used.

Here is a demonstration of how to set content with the jQuery val() methods:

$(“#btn”).click(function(){
	$(“#test”).val(“hello”);
});

This jQuery method also comes with a get/return/callback function. The callback function has two parameters: the index of the current element and the original (old) value. A user then returns the string they wish to use as the new value from the function.

Q29. What is use of $(document).ready()?

A page to be manipulated safely needs the document to be ready. jQuery detects this state of readiness for you. A page document object model (DOM) which is ready for javascript code to execute includes inside $(document).ready(). Code included inside $(window).on("oad",function(){…}) will run once the entire page, not just the DOM, is ready. A developer sometimes can use the shortform $() for $(document).ready().

Example: chaining together the css(), slideup() and slidedown() methods – $("#A1").css("colour","pink").slideup(200).slidedown(200);

Q30. What is chaining in jQuery?

jQuery allows users to chain together actions/methods. Chaining allows users to run multiple jQuery methods within a single statement. This technique of chaining allows us to run multiple jQuery commands, one after the other, on the same elements.

This helps browsers by reducing the time to find the same element more than once. A chain an action user appends the action to the previous action.

Q31. How to get attribute of an element in jQuery?

c

The following example uses how to get the value of the href attribute in a page:

$(“button”).click(function(){
	Alert($(“#w3s”).attr(“href”));
});

Q32. What is the jQuery Unbind() method?

The unbind() method removes event handlers from selected elements. The unbind() function removes all or selected event handlers, or stops specific functions from running when the event occurs. This is used to unbind an event from within itself.

This method works on any event handler attached to jQuery.

$(selector).unbind(event,function,eventObj)

Q33. What is $.each() function do in jQuery?

This function can be used to seamlessly iterate over both objects and arrays. An object with a length property is iterated by a numeric index from 0 to 1. The $.each() function is different from the $(selector).each() which is used to iterate over a jQuery object.

For example:

$.each([50,9],function(index, value){
	Alert(index + “:” +value);
});

This produces two messages:
0: 50
1: 9

Q34. Which is fastest and slowest selector in jQuery?

In jQuery, there are mainly three selectors, which are ID, class, and attribute. Among these, Id selector is the fastest of all, the reason being that ID is supposed to be unique, so the searching stops after ID is found on the Document object model. Whereas, class and attribute search through the entire page to find the required match taking a bit longer then ID selector.

Q35. What is the use of jQuery.data() method?

The data() method gives the user the ability to attached data to or gets data from, within DOM nodes and Javascript objects. When a user uses the data method, the user needs to pass two parameters such as key and a value to be stored.

For example,
$(“mydiv”).data({“name”:”pooja”,”age”:24});

Today, the whole world is embracing the jQuery, companies such as IBM, Microsoft and Google are already using it. jQuery open source project is also running for adding more features in the library. This shows that jQuery will run for a long time. To know completely about jQuery, check our jQuery online interview questions. These interview questions will help you to clear all your doubts and to crack any interviews. Get a look!

Which is better?

jQuery DOJO
It is a JavaScript library It is a JavaScript toolkit. JQuery is licensed by MIT. The dojo is licensed by BSD or AF. It was started at Rochester Institute of Technology in January 2006 by John Resig. It was released in 2004 by Dylan Schiemann, David Schontzler and Alex Russell.
JQuery presents User Interface libraries with many beneficial functionalities Dojo toolkit provides the features of a widget toolkit.
JQuery is used mostly for web application and dynamic web pages. Dojo is used for web-oriented software on desktop, mobile and internet applications.
JQuery is being used by WordPress, BackBone, Wikipedia, etc. Dojo is being used by internet browsers like Internet Explorer, Google Chrome, Safari, etc.
JQuery is lightweight with 19K compressed base libraries. Dojo provides many customizing choices but it is a massive and complex toolkit.
JQuery requires a less network bandwidth than Dojo. Dojo requires a higher network bandwidth than JQuery.

Advantage of jQuery:

  • Open source library: JQuery is an open source library for all types of application. What a developer wants more than this, anyone can use it for their applications without any license or agreement issues.
  • Lightweight: The size of the jQuery core library is just 24kb which can be easily added to any application and hence, increase the performance. The reason behind the lightweight jQuery library is limited functions. Some functions are omitted from the library and some are transferred to plug-ins. So that whenever these functions required, developers can add those plugins in their applications.
  • Limited Coding level: As the slogan of jQuery “few lines of code, do the most things” explains by itself. The use of advanced selectors in jQuery lets the developers write just a few lines of code and obtain the desired result. Thus, jQuery took the JavaScript to a higher level.
  • Browser compatibility: It is the utmost advantage of jQuery, as this is the biggest problem that any developer face in other designs. For example, in JavaScript, when you write code for one browser, it may not run on another browser properly. So, the designers of jQuery fixed this problem and help the developers to write the same code for all browsers.
  • Plug-ins: jQuery provides the thousands of plug-ins to perform the tasks such as validation, animation, field prompt and many more. It doesn't stop here; you can also create your own plug-ins and also can share with other developers. To create the plug-in is very simple, just use the framework given to extending the library.
  • Flexible: jQuery is compact but easy to learn. If you want to understand jQuery, then you just need to give a little bit of your time. You will be able to write the codes and independent widgets very easily after going through a short tutorial on jQuery.
  • jQuery is a fun: jQuery is very powerful and precise language. Using jQuery for programming gives you the desired result very quickly. It solved the many challenges and issues of JavaScript. Many fundamental tools are improved and many new are designed which developers can use to generate next level web applications.
  • Animations: You can easily avail cool effects such as contrast/expand, fade out, etc. in designing the application by writing just a couple of lines of code.

Disadvantages of jQuery:

  • Limited Functionalities: In spite of the powerful library, but sometimes it is necessary to use the raw JavaScript. Functionalities may be limited that depends on how much personalization; you want in your application.
  • Backward compatibility: Sometimes, the new version is not compatible with the previous version. For instance, the newer version has removed some selectors which are previously widely used. This may confine the developers to upgrade their application from an old version to a newer one.
  • Plugins compatibility: Similar to backward compatibility, developers need to check the plugins supported by the newer version before upgrading. Sometimes, the existing plugins are not supported by the newer versions at all. Also, while using multiple plugins on the same page, can encounter some conflicts.

About Author :

  • Author of JQuery Interview Questions

    Sharad Jaiswal

    Sharad Jaiswal is Sr. Web Developer from Noida area. He have rich experience in PHP, Angular Js, React, javascript and Node .If you any query or project on these programming you can drop your enquiry in comment section.

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