JQuery Interview Questions & Answers [2019 Updated]

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Vineet Chaudhary
Vineet Chaudhary
Vineet Chaudhary is a tech junkie with his bachelor in Computer Applications. His interest in the latest technology around the world and his love for writing helped him become a content writer for DinoSoftLabs. In his free time, he spends time with his first love- racing games and simulators.

Article Index

1. Introduction

2. Frequently Asked jQuery Interview Questions and Answers

3. Conclusion

 

Introduction

There are several profiles available for the job post of a development engineer/coder. Ranging from web development to software development and jQuery coder. In case you have been called for an interview for the profile of a jQuery coder, then DinoSoftLabs is the right platform to get a quick recap of jQuery interview questions and answers before you ace the interview!

These are the few questions that you can expect will be asked to you during the interviews. These jQuery interview questions and answers for experienced professionals are also suitable for freshers as well. The jQuery interview questions are a jumbled mixture of all the major topics and doubts that can also be used for the jQuery practical interview part.

 

Here are the top 35 jQuery interview questions and answers you can master:

Question 1. What is jQuery?

jQuery is a Javascript library that has several features which help in traversing and manipulation of HTML documents. Along with this, jQuery also helps with building animations, Ajax, modifying the alignment, and rendering UI effects. This language is also known as the client-side scripting language.

 

Question 2. What are the differences between JavaScript and jQuery?

JavaScript

  • Dynamic programming language, which is weakly typed.
  • It is an interpreted language.
  • The script has to be written by the developer, which takes time.
  • No additional plug-in required.
  • The length of the code is very long.

jQuery

  • Concise and fast JavaScript library
  • Uses resources of JavaScript to makes tasks easy and simple.
  • Only existing jQuery scripts to be added in code as it saves time.
  • jQuery library URL to be added in the header page
  • The lines of code are lesser.

 

Question 3. What are the various features of jQuery?

These are the features of jQuery:

  • AJAX Support- jQuery supports AJAX, which helps in developing a responsive website.
  • Multiple Browser Support- jQuery is supported by several browsers like IE 6.0+, Safari 3.0+, Chrome, and Opera 9.0+
  • Lightweight- The file size of the library is very less-19KB.
  • Event handling- It provides an artistic way to capture various events that take place on the website.
  • Animations- Several in-built animation effects can be used on the websites.

 

Question 4. What are the advantages of jQuery?

jQuery has several advantages, and some of them are:

  • Cross-browser support makes it easier to use anywhere.
  • It helps in the process of event handling and detection.
  • There are tons of plug-ins for all sorts of needs.
  • jQuery helps in keeping the code clear, simple, and reusable.
  • It is an improved and better version of JavaScript.

 

Question 5. What are the ‘selectors’ in jQuery?

In basic language, selectors are used to selecting HTML elements with the help of jQuery. A jQuery selector uses the expressions to find out the same items from a DOM. The items in the DOM are selected by using $() construct along with a string parameter that has CSS selector expression. $() returns 0 or more DOM items on which a user can apply effects.

 

Question 6. What are the different types of Selectors?

Tag Name:

  • ID- Syntax is $(‘#TextId’)- selects elements with ID as TextId.
  • Class- Syntax is $(‘.myclass’)- selects elements with class as myclass.

 

Question 7. What are various methods by which we can add effects in jQuery?

jQuery library has several amazing effects that can be applied easily by a simple configuration. The effects that can be applied are hiding, showing, toggling, fadein, fadeout, and many more. Other methods to provide effects include these:

  • animate( params, [duration, easing, callback] )- for custom animations for HTML elements.
  • fadeIn( speed, [callback] )- this fades the matched elements with the help of adjusting their opacity. fires optional callback after completion.
  • fadeOut( speed, [callback] )- this fades out the matched elements by bringing the opacity to 0. sets display to “none” and fires optional callback once completed.
  • fadeTo( speed, opacity, callback )- this function fades the opacity of matched elements to specified opacity. fires optional callback once completed.
  • stop( [clearQueue, gotoEnd ])- stops all the running algorithms.

 

Question 8. What does jQuery Ajax mean?

AJAX is used as an acronym for Asynchronous JavaScript and XML, and it helps us to load and exchange data without refreshing the browser page. jQuery is a fantastic tool with many AJAX methods that can be used to develop various web applications.

 

Question 9. What is the use of ajax() method?

It sends an asynchronous Http request to the server.

 

Question 10. What do you mean by jQuery Ajax Events?

The events that are fired based on the state of the Ajax request are called Ajax events. These are located in the jQuery libraries.

 

Question 11. What is the purpose of the jQuery Ajax event method ajaxComplete()?

Every time the Ajax completes a request, it triggers an ajaxComplete event, and every handler registered by .ajaxComplete() method gets executed.

 

Question 12. What is the purpose of the jQuery Ajax event method ajaxStart()?

jQuery checks for other outstanding requests whenever Ajax request is to be sent if it’s clear, jQuery triggers the ajaxStart event, and all the handlers registered with .ajaxStart() method gets executed.

 

Question 13. What is the difference between width() vs css(‘width’) in jQuery?

These commands are used to change the width of an element in jQuery. The difference in them is the data type value that is specified from both the functions. In .css(‘width’) we add px in the value whereas no px is added in .width().

 

Question 14. What are Events in jQuery?

The responses we see on interacting with a webpage are called events. jQuery helps in attaching event handlers, and whenever an event occurs, the function is executed.

 

Question 15. What are the different categories in jQuery Events?

The frequent DOM events on the platform are as follows:

  • form
  • mouse
  • keyboard
  • document loading
  • browser

 

Question 16. What is the CSS() method used for in jQuery?

This method helps to get (return) or set style properties for selected items.

 

Question 17. What is the main difference between find and children methods?

The Find method is used to find all levels in the DOM tree. The Child method searches a single level down the DOM tree.

 

Question 18. What is the difference between an ID selector and a class selector in jQuery?

Both the selectors are present in CSS, and as the name suggests, the ID selector uses the ID to select elements, and the class selector uses class. An ID selector is used for a single element, whereas, for a group of items, the class is used provided they have the same CSS class.

 

Question 19. What is the requirement to start jQuery?

The essential thing a person can do to get started with jQuery is by referring to jQuery’s complete library. With this, you get access to all application files.

 

Question 20. What is the difference between document.ready() and onload() methods?

document.ready() is launched when the DOM is loaded, and it does not wait for the resources to load. onload() is launched once DOM and associated resources such as images are loaded.

 

Question 21. What is the meaning of jQuery connect?

It is a plug-in that is used to connect or bind a function from the system together. Connect executes a function when a function from another object is completed.

 

Question 22. Do we need jQuery for bootstrap?

The answer depends on the situation- if you are using CSS part of bootstrap, then jQuery is not needed. In the case of JavaScript plug-ins like tooltips, models, etc., then you need jQuery.

 

Question 23. What does jQuery Mobile mean?

The user interface system that was designed on HTML-5 and is used to make responsive web sites and apps that are accessible on smartphones, tablet, and desktops are called jQuery Mobile.

 

Question 24. What is the difference between jquery.min.js and jquery.js?

In terms of their functioning, both are the same, but jquery.min.js is a compressed version of the jquery.js. In this, the whitespaces and comments are removed, shorter variable names are used, etc. The usage of the compressed version is recommended in a production environment as it increases the efficiency of the webpage.

 

Question 25. What is a queue(), and what are its uses in jQuery?

Delay is a part of the custom effects category in the jQuery. The sole purpose of this effect is to delay the execution of the following items that are present in the queue.

queueName is where the delay time is inserted. It is an “fx’ queue by default, and it is also known as an effects queue.

 

Question 26. Is jQuery HTML functional with both, HTML and XML documents?

No, jQuery HTML does not work for both. It only works for HTML documents.

 

Question 27. What is the major difference between Map and Grep functions from jQuery?

When a user uses $.map(), they have to loop over every element present in the array and modify its value. When they use $.Grep(), it returns a filtered array using filter condition from the existing array.

The basic structure of Map() is:

  • $.map(array, callback(elementofarray, indexinarray))

 

Question 28. What is the difference between prop and attr?

jQuery.attr()- This is used to get the value of an attribute for the first element in a set of matched elements.

jQuery.prop()- This is used to get the value of the property for the first element of a set of matched elements.

 

Question 29. What is the definition of jQuery UI?

It is a set of user interface interactions, effects, themes, and widgets that are built on top of the jQuery JavaScript Library. jQuery UI platform works well with everything- from a highly interactive web application to a simple page.

 

Question 30. What does Qunit mean?

It is an easy-to-use, powerful JavaScript unit testing framework that is used by jQuery, jQuery Mobile projects, and jQuery UI. It has the capability to test any JavaScript code.

 

Question 31. What is the difference between detach() and remove() methods?

detach() method removes the elements but retains them in the memory, whereas .remove() deletes all the jQuery data associated with the elements. Usage of detach() is preferred as it is useful in case the removed elements are needed again in the DOM.

 

Question 32. Can we use a jQuery library for server scripting?

jQuery is functional as a client-side scripting platform and is not compatible with server-side scripting.

 

Question 33. What is CDN?

The full form of CDN is Content Distribution Network or Content Delivery Network. It is a distributed network of servers that are located in multiple data centers on the internet. This helps in providing files at a higher bandwidth, which leads to faster loading time for the webpages. Google, Microsoft, Yahoo are some of the companies that provide free public CDNs.

 

Question 34. What are the advantages of using CDN?

The advantages of CDN are:

  • It helps in saving bandwidth as with CDN; the jQuery framework is loaded faster.
  • This helps to reduce the load from the server.
  • Any website that is visited regularly and uses the jQuery framework gets cached in the system.

 

Question 35. What are jQuery plug-ins?

jQuery plug-ins are source codes that are written in the basic JavaScript file, and these files provide various jQuery methods that are used along with jQuery library methods.

To use a plug-in, it must have a semicolon (;) in the end, and the method used must return a value unless explicitly noted otherwise.

 

Conclusion

Even though jQuery is a very small JavaScript library, it is one of the most used libraries when it comes to web development and providing an entertaining and interactive experience for the web. We hope these jQuery interview questions were helpful for you, and you are prepared for the interview.

If you have any interview questions on jQuery based on your personal experience, comment below, and we’ll update the article to help the future coders.

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