JQUERY INTERVIEW QUESTIONS & ANSWERS PART-1

1) What is jQuery?

JQuery is fast, lightweight and feature-rich client-side JavaScript Library/Framework which helps in to traverse HTML DOM, make animations, add Ajax interaction, manipulate the page content, change the style and provide cool UI effect. It is one of the most popular client-side libraries and as per a survey it runs on every second website.

jQuery is not a programming language but a well written JavaScript code. It is a JavaScript code, which do document traversing, event handling, Ajax interactions and Animations.

2) Why jQuery is needed?

jQuery is needed for the following list:

·         Used to develop browser compatible web applications.

·         Improve the performance of an application.

·         Very fast and extensible.

·          UI related functions are written in minimal lines of codes.

3) Why do we use JQuery?

Due to following advantages.

·         Easy to use and learn.

·         Easily expandable.

·         Cross-browser support (IE 6.0+, FF 1.5+, Safari 2.0+, Opera 9.0+)

·         Easy to use for DOM manipulation and traversal.

·         Large pool of built in methods.

·         AJAX Capabilities.

·         Methods for changing or applying CSS, creating animations.

·         Event detection and handling.

·         Tons of plug-ins for all kind of needs.

4) How JavaScript and JQuery are different?

JavaScript is a language while jQuery is a library built in the JavaScript language that helps to use the JavaScript language.

5) Is JQuery replacement of Java Script?

No. JQuery is not a replacement of JavaScript. JQuery is a different library which is written on top of JavaScript. JQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML.

6) Whether jQuery HTML work for both HTML and XML documents?

No, jQuery HTML only works for HTML documents not for XML Documents.

7) What are the methods used to provide effects?

Some of the effects methods are:

·         Show()

·         Hide()

·         Toggle()

·         FadeIn() and

·         FadeOut()

8) What is the advantage of using minimized version of jQuery?

Efficiency of web page increases when minimized version of jQuery is used.min.js file will be more than 50% less than the normal js file. Reduction in the file size makes the web page faster.

9) Is jQuery is a JavaScript or JSON library file?

jQuery is a library of JavaScript file and it consists of DOM, event effects and the Ajax functions. jQuery is said to be a single JavaScript file.

10) Which operating system is more compatible with jQuery?

Mac, Windows and Linux are more compatible with the jQuery.

11) How can we include jQuery library in ASP.Net project?

Download the jQuery library from jQuery.com and include that reference in the asp.net page.

12) Which command will give a version of jQuery?

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

13) In what scenarios jQuery can be used?

jQuery can be used in following scenarios:

·         Apply CSS static or dynamic.

·         Calling functions on events.

·         Manipulation purpose.

·         Mainly for Animation effects.

14) What is the difference between find and children methods?

Find method is used to find all levels down the DOM tree but children find single level down the DOM tree.

15) What is jQuery connect?

A ‘jQuery connect’ is a plugin used to connect or bind a function with another  function. Connect is used to execute function from any other function or plugin is executed.

16) How to use connect?

Connect can be used by downloading jQuery connect file from jQuery.com and then include that file in the HTML file. Use $.connect function to connect a function to another function.

17) What are the features of jQuery, has been used in web applications?

jQuery uses features like Sliding, File uploading and accordian in web applications.

18) What are the browser related issues for jQuery?

Browser compatibility of jQuery plugin is an issue and needs lot of time to fix it.

19) Whether we need to add jQuery file in both Master and Content page?

jQuery file should be added to the Master page and can use access from the content page directly without having any reference to it.

20) What are the basic selectors in jQuery?

Following are the basic selectors in jQuery:

·         Element ID

·         CSS Name

·         Tag Name

·         DOM hierarchy

21) Can we call C# code behind using jQuery?

Yes, we can call C# code from jQuery as it supports .net application.

22) What is the use jQuery.data method?

jQuery.data methods is used to associate the data with the DOM nodes and the objects. This data method makes the jQuery code clear and concise.

23) What is the use of each function in jQuery?

Each function is used to iterate each and every element of an object. It is used to loop DOM elements, arrays and the object properties.

24) What is the difference between size and length of jQuery?

Size and length both returns the number of element in an object. But length is faster than the size because length is a property and size is a method.

25) Can we add more than one ‘document.ready’ function in a page?

Yes, we can add more than one document.ready function in a page. But, body.onload can be added once in a page.

26) What is the use of jQuery load method?

jQuery load method is a powerful AJAX method which is used to load the data from a server and assign the data into the element without loading the page.

27) Whether our own specific characters are used in place of $ in jQuery?

Yes, we can use our own variable in place of $ by using the method called no Conflict () method.

var sample = $.noConflict()

28) What are the four parameters used for jQuery Ajax method?

The four parameters are

1.      URL - Need to specify the URL to send the request.

2.      type - Specifies type of request(Get or Post).

3.      data - Specifies data to be sent to server.

4.      Cache - Whether the browser should cache the requested page.

29) What is the use of jQuery filter?

The jQuery filter is used to filter the certain values from the object list based on the criteria. Example is to filter certain products from the master list of products in a cart website.

30) Which program is useful for testing jQuery?

QUnit is used to test jQuery and it is very easy and efficient.

31) Which sign is used as a shortcut for jQuery?

Dollar ($) sign is used as a shortcut for jQuery.

32) Is jQuery is a client or server scripting?

jQuery is a client scripting.

33) What is the script build up by jQuery?

jQuery is a Javascript file and it is single javascript file that contains common DOM, event effects and Ajax functions.

34) How can we debug jQuery?

There are two ways to debug jQuery:

Debugger keyword

·         Add the debugger to the line from where we have to start debugging and then run Visual Studio in Debug mode with F5 function key.

·         Insert a break point after attaching the process

35) What are all the ways to include jQuery in a page?

Following are the ways to include jQuery in a page:

·         Local copy inside script tag.

·         Remote copy of jQuery.com.

·         Remote copy of Ajax API.

·         Local copy of script manager control.

·         Embedded script using client script object.

36) What is the use of jQuery.ajax method ()?

jQuery.ajax method is used for asynchronous HTTP requests.

37) Where can we download JQuery?

jQuery javascript can be downloaded from jQuery official website – www.jquery.com

38) Is jQuery is a replacement of JavaScript?

No, jQuery is not a replacement of JavaScript.

39) What is called chaining?

Chaining is used to connect multiple events and functions in a selector.

40) What are the advantages of jQuery?

Following are the advantages of jQuery:

·         Just a JavaScript enhancement.

·         Coding is simple, clear, reusable.

·         Removal of writing more complex conditions and loops.

41) Whether C# code behind can be called from jQuery?

Yes, we can call C# code behind from jQuery.

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

jQuery data method is used to associate data with DOM nodes and JavaScript objects. This method will make a code very concise and neat.

43) What is the difference between onload() and document.ready()?

In a page, we can have only one onload function but we can have more than one document.ready function. Document.ready function is called when DOM is loaded but onload function is called when DOM and images are loaded on the page.

44) Is there any difference between body onload() and document.ready() function?

document.ready() function is different from body onload() function for 2 reasons.

1.      We can have more than one document.ready() function in a page where we can have only one body onload function.

2.      document.ready() function is called as soon as DOM is loaded where body.onload() function is called when everything gets loaded on the page that includes DOM, images and all associated resources of the page.

45) What is the use of jQuery each function?

jQuery each function is used to loop through each and every element of the target jQuery object. It is also useful for multi element DOM, looping arrays and object properties.

46) How method can be called inside code behind using jQuery?

$.ajax can be called and by declaring WebMethod inside code behind using jQuery.

47) Where jQuery code is getting executed?

jQuery code is getting executed on a client browser.

48) What is the method used to define the specific character in place of $ sign?

‘NoConflict’ method is used to reference a jQuery and save it in a variable. That variable can be used instead of Sign.

49) Why jQuery is better than JavaScript?

jQuery is a library used for developing Ajax application and it helps to write the code clean and concise. It also handles events, animation and Ajax support applications.

50) What are the types of selectors in jQuery?

There are three types of selectors in jQuery:

1.      CSS Selector

2.      XPath Selector

3.      Custom Selector

51) What are selectors in jQuery and how many types of selectors are there?

To work with an element on the web page, first we need to find them. To find the html element in JQuery we use selectors. There are many types of selectors but basic selectors are:
 

·         Name: Selects all elements which match with the given element Name.

·         #ID: Selects a single element which matches with the given ID

·         .Class: Selects all elements which match with the given Class.

·         Universal (*): Selects all elements available in a DOM.

·         Multiple Elements E, F, G: Selects the combined results of all the specified selectors E, F or G.

·         Attribute Selector: Select elements based on its attribute value.

52) Which is the fastest selector in jQuery?

ID and Element are the fastest selectors in jQuery.

53) What is the slowest selector in jQuery?

Class selectors are the slowest selectors in jQuery.

54) How do you select element by ID in jQuery?

To select element use ID selector. We need to prefix the id with "#" (hash symbol). For example, to select element with ID "txtName", then syntax would be,

$('#txtName')

55) What does $("div") will select?

This will select all the div elements on page.

56) How to select element having a particular class (".selected")?

$('.selected'). This selector is known as class selector. We need to prefix the class name with "."(dot).
 

57) What does $("div.parent") will select?

All the div element with parent class.

58) What are the fastest selectors in jQuery?

ID and element selectors are the fatest selectors in jQuery.

59) What are the slow selectors in jQuery?

Class selectors are the slow compare to ID and element.

60) How jQuery selectors are executed?

Your last selectors are always executed first. For example, in below jQuery code, jQuery will first find all the elements with class ".myCssClass" and after that it will reject all the other elements which are not in "p#elmID".

$("p#elmID .myCssClass");

61) Which is fast document.getElementByID('txtName') or $('#txtName').?

Native JavaScipt is always fast. jQuery method to select txtName "$('#txtName')" will internally makes a call to document.getElementByID('txtName'). As jQuery is written on top of JavaScript

and it internally uses JavaScript only So JavaScript is always fast.