Top 35 interview questions on JQuery

jquery-interview-questions

We have listed down some of the most frequently asked Interview questions of JQuery. These questions curated by the experts so that you don’t have to go anywhere. Here we will bestow the in-depth knowledge about JQuery so that you can bag down your dream job.

1. Define JQuery?

Answer. JQuery was first released on August 26, 2006, and it is free and open-source software using permissive MIT license. JQuery’s syntax is designed to make it easier to navigate a document, select DOM elements, create animations, handle events, and develop Ajax applications. JQuery also provides developers with the ability to create JavaScript plug-ins.

2. What are the advantages of JQuery?

Answer.

  • It’s like an enhanced JavaScript version, so learning a new syntax has no overhead.
  • It gives hundreds of plug-ins for everything.
  • JQuery has cross-browser support.
  • This would eliminate the need to write complex loops and library calls for DOM scripting.
  • JQuery is capable of keeping the code short, easy to read, straightforward and reusable.

3. Name the methods that provide effects to JQuery?

Answer.

  • Fade In ()
  • Fade out ()
  • Show ()
  • Hide ()
  • Toggle ()

4. What is the difference between the ID selector and class Selector in JQuery?

Answer. If you’ve used CSS, you might know the difference between the ID and the class selector, jQuery is the same. ID selector uses ID for selecting elements, e.g. #element1, while class selector uses CSS for selecting items. When selecting just one element, use the ID selector while selecting a group of elements with the same CSS class as using the class selector. The interviewer is likely to ask you to write code using the ID and class selector. From the point of view of syntax, as you can see, another difference is that the former uses “#” and later uses.” “character.

5. What do you mean by booking?

Answer. If more than one selector shares the same statement, they can be grouped together through a comma-separated list; this enables you to reduce the size of the CSS (every bit and byte is important) and make it more readable. The following snippet applies the same background to the h1, h2, h3 {background: blue;}.

6. Name the compatible operating system with JQuery?

  • Windows
  • Mac
  • Linux

7. How you can read, write and delete cookies in Jquery?

Answer. Using the Dough cookie plugin, we can handle jquery cookies. Dough is user-friendly and features powerful.

  • Create cookie:
$. dough(“cookie_name”, “cookie_value”);
  • Read Cookie:
$. dough(“cookie_name”);
  • Delete cookie:
$. dough(“cookie_name”, “remove”);

8. What do you mean by JQuery connect? And also tell how to use it?

Answer.  A jQuery connect is a plugin for connecting or binding a function to another function. Connect is used from any other function or plugin to perform a function. Through downloading the jQuery link file from jQuery official website, it can be used to include that file in the HTML document. To connect one function to another, you need to use $. connect.

9. Is there any program for testing JQuery? If yes, name it?

Answer.  Yes, there is a program for testing JQuery. QUnit is used to test jQuery and it is very easy and efficient.

10. What do you mean by Jquery UI?

Answer. JQuery UI is a set of jQuery JavaScript Library user interactions, effects, widgets, and themes. JQuery UI works well for highly interactive web applications with a variety of controls or simple date picker pages.

11. What is the use of the HTML() method in JQuery?

Answer. The method jQuery HTML() is used to change the selected elements ‘ entire content. It replaces the content of the selected component with new content.

$(document).ready(function(){
$(“button”).click(function(){
$(“p”).html(“Hello <b>Codersera</b>”);
});
});

12. What is the use of Jquery.each () function?

Answer. The function “jQuery.each()” is a general function that loops through a set (a type of entity or type of array). The index position and value of array-like objects with a length property are iterated. Certain objects are iterated on the properties of their primary value.

Nevertheless, the function “jQuery.each()” works differently from the function $(selector).each() that uses the selector to operate on the DOM component. But both iterate about an element of jQuery.

Syntax:

<jQuery.each(collection, callback(indexInArray, valueOfElement))
< script type = "text/javascript" >
 $(document).ready(function() {
var arr = ["Mary", "John", "Garry", "Tina", "Daisy"];
$.each(arr, function(index, value) {
alert('Position is : ' + index + ' And Value is : ' + value);
});
}); < /script> 

13. How can you debug JQuery?

Answer. There can be two ways to debug JQuery:-

  • Add the debugger to the line from which to debug and run Visual Studio with the F5 function key in debug mode.
  • Insert a breakpoint after attaching the process.

14. Can Jquery be replaceable with JavaScript?

Answer. NO, JQuery is not a replacement for JavaScript.

15. Differentiate between prop and attr?

Answer. JQuery. prop() – It gets a property value in the matched element set for the first element.

JQuery. Attr()– In the matched element set, it gets the value of an attribute for the first element.

Attributes contain additional HTML element information and come in pairs of name=”value”. You can set and specify an attribute for an HTML element when the source code is published.

 For Eg -<input id="txtBox" value="Jquery" type="text" readonly="readonly" /> 

Here, “id”, “type” and “value” are attributes of the input elements.

jquery data atribute

16. Differentiate between $(this) and this keyword in jQuery?

Answer. For many jQuery beginners, it might be a tricky question, but it’s actually the easiest one. $(this) returns a jQuery object, where you can call several jQuery methods, e.g. text() retrieve text, Val() to retrieve the value, etc., while this is the current component, and it is one of the JavaScript keywords to denote the current DOM element in the background. You can’t call this jQuery process until it’s wrapped up $() function i.e. $(this).

17. Where JQuery can be used?

Answer.

  • Manipulation Process
  • Basically for animation purpose
  • Calling functions on events
  • Apply CSS static or dynamic.

18. Differentiate between find and children methods?

Answer. The find() method is used to locate all the descending elements of the selected element and the children() method is used to find all the elements connected to the selected element.

19. Can you write a command that gives the version to JQuery?

Answer. The command $.ui.version returns jQuery UI version.

20. Can you explain bind() vs live() vs delegate() methods in JQuery?

Answer. The bind() method does not attach events to those elements that are added after loading DOM, whereas live() and delegate() methods often attach events to future elements.

The difference between live() and delegate ()methods is that chaining does not work with the live() function. It will only operate on a selector or element while the chaining method of the delegate() can work.

21. Differentiate between Map and Grep function in Jquery?

Answer. In $.map(), each element in an array must be looped and its value changed while the

$.Grep() method returns the filtered array using some filter condition from an existing array. Map()’s fundamental structure is:

1 $.map ( array, callback(elementOfArray, indexInArray) )

Syntax for $.Grep():

1 jQuery $.grep() Method

22. What are JQuery plugins?

Answer. Plugins are a code piece. The jQuery plugin is a code written in a JavaScript standard file. These JavaScript files provide useful methods for jQuery which can be used in combination with methods for the jQuery library. Every form that you use in plugins must end up with a semicolon “;”. Unless otherwise explicitly noted, the method must return an object. This way it produces clean, stable software. You will prefix the filename with jQuery, follow it with the plugin’s name and finish with.js

23. Jquery is a client or server scripting library?

Answer. Client-side Scripting

24. Which sign is used as a shortcut for Jquery?

AnswerDollar($) sign Is used as a shortcut for Jquery.

25. Name two types of CDN?

Microsoft – Load JQuery from Ajax CDN

Google – Load JQuery from Google libraries API

26. What is the use of the JQuery filter?

Answer. The JQuery filter is used based on the criteria to delete those values from the list of items. An example is to filter some products from a cart website’s master list of products.

27. Define the use of JQuery.data() method?

Answer. To connect data with DOM nodes and JavaScript objects, the JQuery data method is used.

28. Define the use of the serialize () method in Jquery?

Answer. The JQuery serialize() method is used to create a text string in standard URL-encoded notation. It serializes the form values so that its serialized values can be used in the URL query string while making an AJAX request.

$(document).ready(function(){
$("button").click(function(){
$("div").text($("form").serialize());
  });
});

29. Differentiate between $(window).load and $(document).ready function in jQuery?

Answer. $(window).load is an event that fires when the page’s full loading of the DOM and other content. After the ready case, this event will be set.

In most cases, as soon as the DOM is fully loaded, the script can be executed. Normally the ready) (is the best place to write your JavaScript code. But there might be some situation wherein the load) (the method you might need to write scripts. For instance, to get an image’s actual width and height.

Once the DOM and all the CSS, images and frames are fully loaded, the $(window). load event will be released.

30. Differentiate between Jquery.size() and Jquery.length?

Answer. The function jQuery.size() gives the maximum number of elements in the set. But the method size() is not favoured because the property jQuery has.length. It does the same thing but it doesn’t have the overhead of a function call for the.length property.

31. What is the use of param() method in Jquery?

Answer. The param() method in jQuery is used to create a serialized representation of an object.

32.  Differentiate between onload() and document.ready()?

Answer. We can only have one onload feature on a page, but we can have more than one file. When DOM is loaded, Document.ready is called, but when DOM and images are loaded on the screen, the onload function is called.

33. Which is the fastest selector in JQuery?

Answer. ID and Element are the fastest selectors in JQuery.

34. What is the slowest selector in JQuery?

Answer. Class selectors are the slowest selector in JQuery.

35. Name the types of selectors in JQuery?

Answer.

  • CSS Selector
  • XPath Selector
  • Custom Selector

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