Top 20 jQuery Interview Questions and Answers

Prasad Kulkarni  Print   6 min read  
26 Apr 2019
20 Jun 2019
1.63K

jQuery is a JavaScript library. It is open source, lightweight and easy to use, simple than JavaScript, it has many inbuilt methods and it can handle events, Html DOM, Ajax and animations too.

  1. What is jQuery?

    jQuery is a JavaScript library. It is open source, lightweight and easy to use, simple than JavaScript, it has many inbuilt methods and it can handle events, Html DOM, Ajax and animations too.

  2. Why use jQuery? What are its advantages?

    There are many reasons behind its popularity; some of them are listed below

    • As it is developed using JavaScript language, it has all features that JavaScript has, with multiple inbuilt methods it is easy to use for validation

    • Event handling is one of the good features of jQuery

    • It’s easy to apply CSS to the controls using jQuery

    • jQuery has good support to AJAX.

    • jQuery has good support to animations as well.

  3. Can you tell me the differences between jQuery And JavaScript?

    The simple and visible difference is, jQuery is a library whereas JavaScript is a language, jQuery is created using JavaScript only, it has methods that use JavaScript language.

  4. How to use jQuery?

    We know jQuery is the collection of JavaScript classes; these classes are bundled and put it in.JS files. To use jQuery, we just need to add the reference of its library to our page.

  5. When to use jQuery?

    Basically, jQuery can be used more than validation part, jQuery has a rich set of methods and events that can be used to handle CSS, controls and page design, jQuery also has good support to animations so it is a good alternative to flash plugins

  6. What is CDN?

    It’s a large network of shared servers, use to distribute some contents. It’s known as ‘Content Distribution Network’, if we use CDN to load libraries, it loads fasters and performance will get improve. Microsoft, Google, and jQuery give you jQuery library CDN.

  7. Can I use JavaScript and jQuery on same page?

    The answer is YES, we can use JavaScript and jQuery on the same page, to use jQuery, we need to add.JS library reference on to the page, whereas for JavaScript is directly supported by browser only.

  8. What is min.js and why it is used?

    min.js is a minified version of jQuery will mainly be introduced to enhance application performance. As the Size of the minified jQuery file is smaller than normal jQuery file it loads faster than a normal file.

  9. What is jQuery UI?

    jQuery UI is a JavaScript library, basically, it is a user interface portal that is built using JavaScript and can be easily added in new and existing web applications it contains interactive widgets and effects, and we can build rich UI and highly interactive applications using it. It is free and open source.

  10. What is the difference between jQuery UI and jQuery?

    jQuery UI is built using JavaScript, but upon jQuery so to use jQuery UI you need must include jQuery, jQuery is the library built on pure JavaScript

  11. Can we debug jQuery? If yes, how can we do that?

    jQuery can be debugged easily using the following ways:

    • using a debugger; keyword: Add debugger; keyword just before the line where you want to debug

    • using Breakpoint: If you have visual studio then you can place a breakpoint on the line where you want to start debugging

  12. Which is the performance responsive selector?

    The elements which are selected using ID are the performance responsive selector as the ID is unique throughout the rendered page

  13. Which is the slow selector in jQuery?

    Class selectors are slower than id selector, so the slow selector is a class selector.

  14. What is caching in jQuery?

    We know cache is the temp memory that store data, each time when access any page it accesses cache and load data from there only, it will boost application performance, the same concept applies to jQuery we can cache jQuery elements and use them instead of re-querying or re-executing methods/property on DOM

     
     var $controlcahce = $("#button1")
     $controlcahce.css("color", "red");
     $controlcahce.text("text set!");
    

    Code Snippet Explanation: In the above snippet, we have selected button1with its ID and store it in a controlcahce variable, later on, we can use it directly to set CSS value or set text

  15. What are the jQuery get methods?

    jQuery has more powerful ways of manipulating and changing HTML elements and attributes. Following functions are known as jQuery Get methods

    • text()

    • html()

    • val()

  16. What is the difference between “this” and “$(this)” In jQuery?

    To refer current element, we use ‘this’ element, in traditional, we use ‘this’ object and in jQuery, we use ‘$(this)’ this new object will also help us to explore and support jQuery methods also. No doubt you can use ‘this’ in jQuery also. Look at below sample

     
     //Using ‘this’
     $(document).ready(function () {
     $('#id1').click(function () {
     alert(this.innerText);
     });
     });
     //Using $(this)
     $(document).ready(function () {
     $('# id1').click(function () {
     alert($(this).text());
     });
    

    Code Snippet Explanation: above snippet shows, we can use ‘this’ object in jQuery also but if we use ’ $(this)’ then we can have access to jQuery methods

  17. What is the difference between ‘length’ and ‘size’ in jQuery?

    Both are return numbers and used to find element existence, element value length, etc., but the length is much faster than size as the length is property and size as the method.

  18. What are the supported methods to Ajax in jQuery?

    Below methods are used to deal with Ajax in jQuery

    • Get()

    • Post()

    • GetJSON()

    • Ajax()

  19. Can we use multiple document.Ready() function?

    Yes, we can use multiple documents. Ready function on a web page, this is helpful when we need to execute a large jQuery code and split it into multiple files.

  20. What is the difference between .remove() and .detach() methods in jQuery.

    Basically, both the methods are used to remove data from jQuery DOM, but .detach() method retains all removed data associated with removed elements so that it can be used later.

Summary

I hope these questions and answers will help you to crack your jQuery Interview. These interview Questions have been taken from our new released eBook jQuery Interview Questions and Answers. 

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