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jQUERY INTERVIEW QUESTIONS :

Q1. What is jQuery?

jQuery is a JavaScript library that simplifies JavaScript and AJAX programming. JavaScript is used to add interactivity and dynamic content to web pages. AJAX (Asynchronous JavaScript and XML) is used for handling external data asynchronously through JavaScript, without refreshing the whole page.

jQuery emphasizes the interaction between JavaScript and HTML. jQuery contains all the common DOM, event, effects, and Ajax functions in a single JavaScript file.

The jQuery file needs to be included in the file which is going to use the jQuery functionality.

jQuery provides a new class called jQuery without extending the built-in JavScript classes which acts as a wrapper around objects for providing them the extended operations.

Q2. Advantages of jQuery?

The advantages of using jQuery are:

JavaScript enhancement without the overhead of learning new syntax

Ability to keep the code simple, clear, readable and reusable

Eradication of the requirement of writing repetitious and complex loops and DOM scripting library calls

Q3. Explain the features of jQuery.?

Features of jQuery are :

Effects and animations

Ajax

Extensibility

DOM element selections functions

Events

CSS manipulation

Utilities - such as browser version and the each function.

JavaScript Plugins

DOM traversal and modification.

Q4. Explain the concepts of "$ function" in jQuery with an example.?

The type of a function is "function".

There are a lot of anonymous functions is jquery.

$(document).ready(function() {});

$("a").click(function() {});

$.ajax({

url: "someurl.php",

success: function() {}

});

Q5. Why is jQuery better than javascript?

jQuery is great library for developing ajax based application.

It helps the programmers to keep code simple and concise and reusable.

jQuery library simplifies the process of traversal of HTML DOM tree.

jQuery can also handle events, perform animation, and add the ajax support in web applications.

Q6. Explain how jQuery Works.?

<html>

<head>

// You can write the code here

</script>

</head>

<body>

<a href="http://careerride.com/">CareerRide</a>

</body>

</html>

Q7. When can you use jQuery?

jQuery can be used to for developing ajax based applications

It can be used to keep the code simple, concise and reusable.

It simplifies the process of traversal of HTML DOM tree.

It can also handle events, perform animation, and add the ajax support in web applications.

Q8. What does dollar sign($) means in Jquery?

Dollar sign is nothing but it's an alias for Jquery. Take a look at below jquery code

$(document).ready(function(){

});

Over here $ sign can be replaced with "jQuery " keyword.

jQuery(document).ready(function(){

});

Q9. How is body onload() function is defferent from document.ready() functon used in Jquery?

Document.ready() function is different from body onload() function because off 2 reasons.

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

Q10. What is Jquery UI?

JQuery UI is a library which is built on top of JQuery library. JQuery UI comes with cool widgets, effects and interaction mechanism.

See below page on this site. Date Picker control used in this page to select date is an example of JQuery UI.

Q11. Name some of the methods of Jquery used to provide effects?

Some of the common methods are :

1. Show()

2. Hide()

3. Toggle()

4. FadeIn()

5. FadeOut()

Q12. what are the different type of selectors in Jquery?

There are 3 types of selectors in Jquery

1. CSS Selector

2. XPath Selector

3. Custom Selector

Q13. How can you select all elements in a page using Jquery?

$("*").css("border", "2px dotted red");

</script>

Q14. How can you select all elements in a page using jQuery?

To select all elements in a page, we can use all selectors, for that we need to use *(asterisk symbol).

$("*").css("border", "2px dotted red");

</script>

The above code will select all elements of the web page and apply border width as 2 pixel, style as dotted and color as red.

Q15. What is the Difference between Jquery-X.X.X.js and Jquery.X.X.X-min.js?

In terms of functionality, there is no difference between the jQuery-x.x.x.js and jQuery-x.x.x-min.js (also called minified version). However this can play a vital role in the performance of the web page.

Q16. How it affects the performance?

jQuery-1.4.4.js file size is 178 KB as against its minified version jQuery-1.4.4-min.js that is only 76.7 KB in size. So when your page loads in the client?s browser if you are not using minified version, it loads 178 KB file that takes more time to load than 76.7 KB.

Q17. What is CDN?

CDN Stands for Content Distribution Network or also called Content Despan style=livery Network is a group of computers placed at various points connected with network containing copies of data files to maximize bandwidth in accessing the data. In CDN a client access a copy of data nearer to the client location rather than all clients accessing

from the one particular server. This helps to achieve better performance of data retrieval by client.

There are two leading CDNs available that hosts jQuery files.

Microsoft - To load jQuery from Microsoft AJAX CDN

jQuery file can be loaded from Microsoft AJAX CDN. For more details, go to http://www.asp.net/ajaxlibrary/cdn.ashx.

You will need to keep following tags in your page.

Google - To load jQuery from Google Libraries API

jQuery file can be loaded from Google CDN for more details, go to http://code.google.com/apis/libraries/devguide.html. You will need to keep following tag in your page.

What’s relationship between JavaScript and ECMAScript? - ECMAScript is yet another name for

JavaScript (other names include LiveScript). The current JavaScript that you see supported in browsers is ECMAScript revision 3.

Q18. What are JavaScript types?

Number, String, Boolean, Function, Object, Null, Undefined

Q19. How do you convert numbers between different bases in JavaScript?

Use the parseInt() function, that takes a string as the first parameter, and the base as a second parameter. So to convert hexadecimal 3F to decimal, use parseInt ("3F", 16);

Q20. What does isNaN function do?

Return true if the argument is not a number.

Q21. What is negative infinity?

It’s a number in JavaScript, derived by dividing negative number by zero.

What boolean operators does JavaScript support?

&&, || and !

Q22. What does "1"+2+4 evaluate to?

Since 1 is a string, everything is a string, so the result is 124.

Q23. How about 2+5+"8"?

Since 2 and 5 are integers, this is number arithmetic, since 8 is a string, it’s concatenation, so 78 is the result.

Q24. What looping structures are there in JavaScript?

for, while, do-while loops, but no foreach.

Q25. How do you create a new object in JavaScript?

var obj = new Object(); or var obj = {};

Q26. How do you assign object properties?

obj["age"] = 17 or obj.age = 17.

Q27. What’s a way to append a value to an array?

arr[arr.length] = value;

Q28. What is this keyword?

It refers to the current object.

Is jQuery a library for client scripting or server scripting?

Client scripting

Q29. Is jQuery a W3C standard?

Q30. What are jQuery Selectors?

Selectors are used in jQuery to find out DOM elements. Selectors can find the elements via ID, CSS, Element name and hierarchical position of the element.

Q31. The jQuery html() method works for both HTML and XML documents?

It only works for HTML.

Q32. Which sign does jQuery use as a shortcut for jQuery?

$(dollar) sign.

Q33. What does $("div") will select?

It will select all the div element in the page.

Q34. What does $("div.parent") will select?

All the div element with parent class.

Q35. What is the name of jQuery method used for an asynchronous HTTP request?

jQuery.ajax()

Q36. What is Jquery?

JQuery is Java Script library or Java Script Framework which helps in how to traverse HTML documents, do some cool animations, and add Ajax interaction to any web page. It mainly helps programmer to reduce lines of code as huge code written in Java Script, can be done easily with JQuery in few lines.

Q37. What does dollar Sign ($) means in JQuery?

Dollar Sign is nothing but it's an alias for JQuery. Take a look at below jQuery code

$(document).ready(function(){

});

Over here $ sign can be replaced with "jQuery " keyword.

jQuery(document).ready(function(){

});

Q38. How is body onload() function is different from document.ready() function used in jQuery?

Document.ready() function is different from body onload() function because off 2 reasons.

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

Click below link to get mostly asked jQuery interview question.

http://jquerybyexample.blogspot.com/2011/08/mostly-asked-jquery-interview-questions.html

Q39. What are the steps you need to follow to use jQuery in ASP.Net project?

It's really simple. One just need to add reference of javascript file(.js). Go to Jquery.com and download the latest version of jQuery. When download is completed, there is a "jQuery-1.3.2.js" in the folder. Include this file

and you good to go now for JQuery.

Note : 1.3.2 denotes the library version.. It can be vary depending upon the version of Jquery you download.

Q40. What is JQuery UI?

JQuery UI is a library which is built on top of JQuery library. JQuery UI comes with cool widgets, effects and interaction mechanism.

See below page on this site. Date Picker control used in this page to select date is an example of JQuery UI.

Q41. What are features of JQuery or what can be done using JQuery?

Features of Jquery

1. One can easily provide effects and can do animations.

2. Applying / Changing CSS.

3. Cool plugins.

4. Ajax support

5. DOM selection events

6. Event Handling

Q42. Name some of the methods of JQuery used to provide effects?

1. Show()

2. Hide()

3. Toggle()

4. FadeIn()

5. FadeOut()

Q43. What are the different type of selectors in Jquery?

There are 3 types of selectors in Jquery

1. CSS Selector

2. XPath Selector

3. Custom Selector

Q44. What are the advantages of JQuery ?

There are many advantages with JQuery. Some of them are :

. It is more like a JavaScript enhancement so there is no overhead in learning a new syntax.

. It has the ability to keep the code simple, readable, clear and reusable.

. It would eradicate the requirement for writing complex loops and DOM scripting library calls.

Q45. How can you select all elements in a page using jQuery?

To select all elements in a page, we can use all selectors, for that we need to use *(asterisk symbol).

$("*").css("border", "2px dotted red");

</script>

The above code will select all elements of the web page and apply border width as 2 pixel, style as dotted and color as red.

Q46. What is jQuery?

jQuery is not a language but it is a well written JavaScript code, As quoted on official jQuery website “it is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development.“

In order to work with jQuery you should be aware of basics of JavaScript, HTML and CSS.

It was released in January 2006 at BarCamp NYC by John Resig.

Licensing:

It is free, open source software Dual-licensed under the MIT License and the GNU General Public License. Microsoft has integrated jQuery officially into its IDE Visual Studio 2010 and jQuery intellisense is available in Visual Studio 2010 now.

Q47. Why jQuery?

jQuery is very compact and well written JavaScript code that increases the productivity of the developer by enabling them to achieve critical UI functionality by writing very less amount of code.

It helps to

# Improve the performance of the application

# Develop most browser compatible web page

# Implement UI related critical functionality without writing hundreds of lines of codes

# Fast

# Extensible – jQuery can be extended to implement customized behavior

Other advantages of jQuery are

# No need to learn fresh new syntax's to use jQuery, knowing simple JavaScript syntax is enough

# Simple and Cleaner code, no need to write several lines of codes to achieve complex functionality.

Q48. Where to download jQuery from?

http://www.jquery.com/

Q49. How to use jQuery?

jQuery usually comes as a single JavaScript file containing everything comes out of the box with jQuery. It can be included within a web page using the following mark-up:

To load local jQuery file

Q50. Do I need to refer jQuery file both in Master page/base page/template page and content page?

No, master page/base page/ template page basically helps to create consistent layout for the page in the application. In case you have referred the jQuery file in master page/base page/ template page that cause rendering the file in the browser, you do not need to refer jQuery file the content page again.

In summary, there should not be more than one <script> tag with jQuery file reference in the source code of the rendered web page in the browser.

Q51. What is the difference between jQuery-x.x.x.js and jQuery.x.x.x-min.js” ?

Q52. How it affects the performance?

Q53. Which version of jQuery file should be used?

In most of the recent releases so far, the core functionality of jQuery remains same however some more cool and better features are added. Ideally you should use the latest jQuery files available on the jQuery.com website. By doing this you ensure that your earlier functionality will still work and you can use new features available as part of the new release.

Q54. What is CDN?

CDN Stands for Content Distribution Network or also called Content Delivery Network is a group of computers placed at various points connected with network containing copies of data files to maximize bandwidth in accessing the data. In CDN a client access a copy of data nearer to the client location rather than all clients accessing

from the one particular server. This helps to achieve better performance of data retrieval by client.

There are two leading CDNs available that hosts jQuery files.

Microsoft - To load jQuery from Microsoft AJAX CDN

jQuery file can be loaded from Microsoft AJAX CDN. For more details, go to http://www.asp.net/ajaxlibrary/cdn.ashx. You will need to keep following tags in your page.

Google - To load jQuery from Google Libraries API

jQuery file can be loaded from Google CDN for more details, go to http://code.google.com/apis/libraries/devguide.html. You will need to keep following tag in your page.

Q55. Why to load jQuery file from CDN?

You may ask that if we can load the jQuery file from our own server why to load it from the CDNs. The answer is logical and very simple. The browser behavior is that whenever it loads any webpage, it keeps related files (eg. Javascript file, CSS file and Images) used for that page into its cache (also called history). When next time the user browses any web page, browser loads only those files that are new or modified and is not available in the browser cache or history. In this way, browser improves its performance and loads the page.

The possibility is that if more and more websites are using CDNs, the user might have already browsed some other web pages that is using CDNs jQuery file and that file may have into browser cache; so when user browse your page and you are also using CDNs file, the older cached version of jQuery file will be used. In this way your page will load faster as browser will not have to load the jQuery file for your page again.

The benefit

1. Faster page load as jQuery file need not to be downloaded

2. Saves your bandwidth as jQuery file is not loaded from your server

3. Scalable - generally CDNs place these files on the servers located at different geographical locations of the world so that they load faster so irrespective of from where your user is browsing your page, your application runs well.

Q56. What if the latest jQuery version is available and I am still referring older version of jQuery file from CDNs?

Do not worry about it, it?s a general promise made by CDNs that they will remain hosting the older version of the files on the same location where they had initially released; so even if newer version of the files are released, the older version remains there on the CDNs and your web page still works.

Q57. How to load local jQuery file in case CDN is not available?

Sometimes, it may happen that the CDN you have used to load the jQuery file is not available (it rarely happens, however anything is possible, isn?t it?); in that case you should load your local jQuery file that is available on your server so that all jQuery related functionality still work on your page.

Write following lines of code

if (typeof jQuery == 'undefined') {

document.write(unescape("%3Cscript src='/Script/jquery-1.4.1.min.js' type='text/javascript' %3E%3C/script%3E"));

}//]]>

</script>

Replace bolded path with your own jQuery file path on the server. In the above code, first line tries to load the jQuery file from CDN, if browser could load the file successfully, “jQuery” variable will ndiv class=ot be undefined and next script will not run otherwise next script will run that will write the script tag to load the jQuery file from your server.

Q58. How to execute jQuery code?

1. As and when page loads, execute the jQuery code

$(function () {

$("#div1").css("border", "2px solid green");

});

</script>

$("#div1").css("border", "2px solid green");

</script>

The benefit of executing jQuery code in this way is that it doesn?t wait the whole page to load completely, so in case you want user to see the effects as soon as the corresponding elements are loaded, you can use this.

However the disadvantage is that if the element on which jQuery has to execute has not loaded then it will error out or you will not get desired result; so while using this way of executing jQuery code, you will have to make sure that the element on which you want to work with jQuery is loaded first (you can place your jQuery code right after your HTML element).

Q59. . Execute jQuery only when the complete DOM objects (the complete page has been loaded). You will have to wrap your code in .ready function.

$(document).ready(function () {

$("#div1").css("border", "2px solid green");

});

</script>

This is the better and safer way to execute jQuery. This makes sure that jQuery code will execute only if complete page has been loaded in the browser so you are rest assured that user will not see any undesired behavior on the page.

As a developer, the decision of where and how to write jQuery code lies on you. I prefer to use 2nd method as it ensures that my complete page is loaded in the browser and I am ready to play with any element available on the page.

jQuery Core

jQuery accepts a string enclosed with double quote (“”) that can contain a CSS selector which is used to match a set of elements ospan class
=n the web page.

jQuery code can start with either “jQuery” word or a “$” (dollar symbol). Take a look at below code snippet

$(function () {

jQuery("#div1").css("border", "2px solid red");

});

</script>

$(function () {

$("#div1").css("border", "2px solid green");

});

</script>

Both above code snippets are functionally same and do the same thing. So you can either user jQuery or $ when you are writing jQuery code.

Q60. How to give alert message in jQuery on a Button Click ?

Hi all,

First, include jQuery in your application.

Drop a textbox in your .aspx page:-

include a button also:-

<asp:Button ID="Button1" runat="server" Text="get"/>

Now, here's the script:-

$(document).ready(function () {

$('#Button1').click(function () {

alert($('#inputField').attr("value"));

});

</script>

Q61. What are Selectors in jQuery mean ?

Generally in HTML, if we need to work with any control on a web page we need to find the control. For that we use document.getElementByID or document.getElementByName. But in jquery we do it using Selectors.

Using this selectors we can select all the controls as well using a symbol (* )

A sample code snippet can be of this form

$("*").css("border", "10px red");

</script>

This will make all the borders in the web page with a width of 10 pixel and color as red.

Q62. Is it good to load jquery from CDN(Content delivery network) ?

Yes, it is always good to load your jquery from content delivery network. It provides some benefits like :-

(1) Caching - It means that if any previously visited site by user is using jQuery from Google CDN then the cached version will be used. It will not be downloaded again.

(2) Reduces load - It reduces the load on your web server as it downloads from Google server's.

Example :-

src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js">

</script>

Q63. Do we need to add the JQuery file both at the Master page and Content page as well?

No, if the Jquery file has been added to the master page then we can access the content page directly without adding any reference to it.

This can be done using this simple example

Q64. What is the advantage of using the minified version of JQuery rather than using the conventional one?

The advantage of using a minified version of JQuery file is Efficiency of the web page increases.

The normal version jQuery-x.x.x.js has a file size of 178KB

but the minified version jQuery.x.x.x-min.js has 76.7 KB.

The reduction in size makes the page to load more faster than you use a conventional jQuery file with 178KB

Q65. What is CDN and how jQuery is related to it?

CDN - It stands for Content Distribution Network or Content Delivery Network.

Generally, a group of systems at various places connected to transfer data files between them to increase its bandwidth while accessing data. The typical architecture is designed in such a way that a client access a file copy from its nearest client rather than accessing it from a centralized server.

So we can load this jQuery file from that CDN so that the efficiency of all the clients working under that network will be increased.

Example :

We can load jQuery from Google libraries API

Q66. Can we select a element having a specific class in jQuery ?

Yes, we can select an element with a specific class, we use the class selector.The class name must contain the prefix as "." (dot).

$(".class1").css("border", "2px solid red");

</script>

Above code will select all the elements of the webpage containing the class as "class1" and apply the css style border width as 2 Pixel, style as solid and color as red.

Q67. What is the use of Delegate() Method in jQuery?

The delegate() method can be used in two ways.

1) If you have a parent element, and you want to attach an event to each one of its child elements, this delegate() method is used.

Ex:Un-ordered List

Instead of attaching an event to each <li> element, you can attach a single event to <ul> element.

Example:

$("ul").delegate("li", "click", function(){

$(this).hide();

});

2) When an element is not available on the current page, this method is used.

.live() method is also used for the same purpose but, delegate() method is a bit faster.

Example:

$("ul").delegate("li", "click", function(){

$(this).hide();

});

This will hide any list items that are not currently available on the page. They may be loaded via an Ajax request and then append to it.

Using .bind() or .click() methods, you would have to manually attach events to these new list items once they are added.

Q68. Which sign does jQuery use as a shortcut for jQuery?

NOTE: This is objective type question, Please click question title for correct answer.

Q69. JQuery is a client scripting.

NOTE: This is objective type question, Please click question title for correct answer.

Q70. Can be used JQuery with AJAX?

NOTE: This is objective type question, Please click question title for correct answer.

Q71. JQuery is JavaScript Library or JSON Library?

JQuery is a javascript library not JSON Library. Jquery library is single JavaScript file that contains Common DOM, event effects and Ajax functions.

"JQuery is a library of javascript function."

For more Info: http://jquery.com/

What does .size() method of jquery return ?

Posted by: Akiii

.size() method of jquery returns number of element in the object. That means that you can count the number of elements within an object.

For example :-

$(document).ready(function(){

var Count = $("div").size();

alert(Count);

});

Q72. What is the difference between jquery.size() and jquery.length ?

jquery.size() and jquery.length both returns the number of element found in the object. But, jquery.length is faster than jquery.size() because size() is a method but length is a property .

So, there is always an overhead in calling a function.

Q73. How to set Page Title using jQuery ?

$(function(){

$(document).attr("title", "Dotnet Funda");

});

Q74. How will you Encode/Decode URL in jQuery ?

In jquery, you can use the following functions to encode and decode url :-

encodeURIComponent(url) and decodeURIComponent(url)

You have to pass the complete url with parameterized value in the function and in return it will encode/decode you url for you !

Q75. What is the use of jQuery Connect?

It is used to connect or bind a function to another function.It is use to execute a function whenever

a function from another object is executed.

e.g.

function FirstFunction(){

this.Func1 = function(){

execute1 = 'A class';

}

var firstFunc = new FirstFunction();

function SecondFunction(){

this.Func2 = function(){

execute2 = 'Another Class';

}

var secondFunc = new SecondFunction();

$.connect(firstFunc,'Func1',secondFunc,Func2);

In this case whevever we invoke secondFunc.Func2,firstFunc.Func1 will also gets executed indicating that

Func2 of object secondFunc has been associated/ connected to Func1 of object firstFunc

Q76. What is the use of jQuery disconnect?

It is used to disconnect a function to another function.It is the opposite of $.connect.

e.g.

$.disconnect(firstFunc,'Func1',secondFunc,Func2);

will disconnect Func1 from Func2 where Func1 is the reference function and Func2 is connected one.

Q77. What is the use of jQuery disconnectAll?

It is used to disconnect all the connected functions.

e.g.

$.disconnectAll(firstFunc,'Func1');

will disconnect all the connected function from the reference function Func1.

Q78. What are the minimal/must steps needed to execute JQuery?

1.Wait for the DOM of the page to be ready.

2.Finds the appropriate HTML elements that needs to be acted on by using selector.

3.Add event handlers.

e.g.

//Step 1: Wait for the DOM of the page to be ready.

$(document).ready(function ()

{

//Step 2: Finds the appropriate HTML elements that needs to be acted on by using selector

var btnObject = $('#btnSayHello');

//Step 3: Add event handlers (Here click events)

btnObject.click(function ()

{

alert("Hello World...My First JQuery Program");

});

Q79. How to debug JQuery?

1.Placing debugger keyword

Add the keyword debugger to the line from where we want to start the debugging and then run the Visual Studio in Debug mode by pressing F5 or using the Debug button.

e.g.

$(document).ready(function ()

{

var btnObject = $('#btnSayHello');

debugger;

btnObject.click(function ()

{

alert("Hello World...My First JQuery Program");

});

</script>

Q80. .Inserting a break point after attaching worker process

Press ALT + CTRL + P or tools -> AttachProcess then choose w3wp.exe .

Q81. What are the ways by which we can include JQuery in our page?

1.Refer to a local copy using the <script> tag

2.Refer to a remote copy on JQuery.com or the remote copy in the Google AJAX API

3.Refer to a local copy using Script Manager Control

4.Refer to an embedded script using the ClientScript object

Q82. How to invoke Jquery function from code behind?

Suppose we want to change the background color of a div tag from the code behind upon button click.In code behind write the below

protected void btnChangecolor_Click(object sender, EventArgs e)

{

string script = "<script type=\"t/divext/JavaScript\" language=\"javascript\">ChangeDivBackgroundcolor();</script>";

Page.ClientScript.RegisterStartupScript(this.GetType(), "ChangeColor", script);

}

The aspx file will be as under

function ChangeDivBackgroundcolor()

{

var divObject = $('#divTest');

divObject.css("background-color", "cyan");

}

</script>

</head>

<body>

<div>

<asp:Button ID="btnChangecolor" runat="server" Text="Say Hello" onclick="btnChangecolor_Click" />

</div>

<div id="divTest">Change the color of this div</div>

</form>

</body>

</html>

Q83. What is the significance of document.ready()?

It indicates that the DOM of the page is ready and we can start manipulating the DOM elements even though other parts

of the page content(e.g. images/other external resources) are not fully loaded.As soon as the DOM is loaded,

everything inside the (document).ready() should be load even before the page contents are loaded.

Q84. Why is JQuery faster than Javascript at execution time?

The onLoad function for the window object executes after the entire page is fully loaded.Untill DOM tree is completely created and all images/other associated resources (like audio files,video files etc) are fully loaded,this onLoad function is never executed and hence the script execution needs to wait till the page is loaded.

But the document.ready() method of JQuery indicates that the DOM of the page is ready and we can start manipulating the DOM elements even though other parts of the page content(e.g. images/other external resources) are not fully loaded.As soon as the DOM is loaded, everything inside the (document).ready() should be load even before the page contents are loaded.

It is because of this reason that JQuery code runs faster

Q85. What is jQuery ?

It's very simple but most valuable Question on jQuery means jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, animating, event handling, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript. Jquery is build library for javascript no need to write your own functions or script jquery all ready done for you

Q86. How you will use Jquery means requirement needed for using jquery?

Nothing more need to do just olny download jquery library(.js file) from any of the jquery site Download jquery and just linked with your html pages like all other javascript file

like below :

Code:

< script src="jquery.js" language="javascript" type="text/javascript">

Q86. what the use of $ symbol in Jquery?

$ Symbol is just replacement of jquery means at the place of $ you may use jquery hence $ symbol is used for indication that this line used for jquery

Q87. How do you select an item using css class or ID and get the value by use of jquery?

If an element of html like < div> , < p> or any tag have ID MyId and class used MyClass then we select the element by below jquery code

Code:

$('#MyId') for ID and for classs $('.MyClass')

and for value

Code:

var myValue = $('#MyId').val();

// get the value in var Myvalue by id

Or for set the value in selected item

Code:

$('#MyId').val("print me");

// set the value of a form input

Q88. How to get the server response from an AJAX request using Jquery?

When invoking functions that have asynchronous behavior We must provide a callback function to capture the desired result. This is especially important with AJAX in the browser because when a remote request is made, it is indeterminate when the response will be received.

Below an example of making an AJAX call and alerting the response (or error):

Code:

$.ajax({

url: 'pcdsEmpRecords.php',

success: function(response) {

alert(response);

error: function(xhr) {

alert('Error! Status = ' + xhr.status);

}

});

Q89. How do you update ajax response with id " resilts"?

By using below code we can update div content where id 'results' with ajax response

Code:

function updateStatus() {

$.ajax({

url: 'pcdsEmpRecords.php',

success: function(response) {

// update div id Results

$('#results').html(response);

}

});

}

Q90. How do You disable or enable a form element?

There arspan style=e two ways to disable or enable form elements.

Set the 'disabled' attribute to true or false:

Code:

// Disable #pcds

$('#pcds').attr('disabled', true);

// Enable #pcds

$('#pcds').attr('disabled', false);

Add or remove the 'disabled' attribute:

// Disable #pcds

$("#pcds").attr('disabled', 'disabled');

// Enable #x

$("#pcds").removeAttr('disabled');

Q91. How do you check or uncheck a checkbox input or radio button?

There are two ways to check or uncheck a checkbox or radio button.

Set the 'checked' attribute to true or false.

Code:

// Check #pcds

$('#pcds').attr('checked', true);

// Uncheck #pcds

$('#pcds').attr('checked', false);

Add or remove the 'checked' attribute:

// Check #pcds

$("#pcds").attr('checked', 'checked');

// Uncheck #pcds

$("#pcds").removeAttr('checked');

Q92. How do you get the text value of a selected option?

Select elements typically have two values that you want to access. First there's the value to be sent to the server, which is easy:

Code:

$("#pcdsselect").val();

// => 1

The second is the text value of the select. For example, using the following select box:

Code:

</select>

If you wanted to get the string "Mr" if the first option was selected (instead of just "1"), you would do that in the following way:

Code:

$("#mpcdsselect option:selected").text();

// => "Mr"

Q93. What is jQuery?

Latest answer: jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML.............

Q94. Advantages of jQuery

Latest answer: The advantages of using jQuery are: JavaScript enhancement without the overhead of learning new syntax............

Q95. Explain the features of jQuery.

Latest answer: Features of jQuery are :

Effects and animations

Ajax

Extensibility.............

Q96. Why is jQuery better than javascript?

Latest answer: jQuery is great library for developing ajax based application.

It helps the programmers to keep code simple and concise and reusable..............

Read answer

Explain how jQuery Works.

Latest answer: <html>

<head>

Read answer

Q97. When can you use jQuery?

Latest answer: JQuery can be used to

apply CSS

call functions on events

traverse the documents...................

Read answer

Q98. What is jQuery Selectors? Give some examples.

jQuery Selectors are used to select one or a group of HTML elements from your web page.

jQuery support all the CSS selectors as well as many additional custom selectors.

jQuery selectors always start with dollar sign and parentheses: $()

There are three building blocks to select the elements in a web document.

1) Select elements by tag name

Example: $(div)

It will select all the div elements in the document.

2) Select elements by ID

Example: $(#xyzid”)

It will select single element that has an ID of xyzid

3) Select elements by class

Example: $(“.xyzclass”)

It will select all the elements having class xyzclass

Q99. How can we give face effect in jQuery?

In jQuery we have three methods to give the fade effect to elements: fadeIn, fadeOut and fadeTo

This methods change the opacity of element with animation.

Syntax:

$(selector).fadeIn(speed,callback)

$(selector).fadeOut(speed,callback)

$(selector).fadeTo(speed,opacity,callback)

“speed” can be one of following values : “slow”, “fast”, “normal” or milliseconds

“opacity” specify the value that allows the fading to given opacity.

“callback” is the function which we want to run once the fading effect is complete.

For example

$("clickme").click(function(){

$("mydiv").fadeTo("slow",0.50);

});

$("clickme").click(function(){

$("mydiv").fadeOut(3000);

});.

Q100. Explain the animate function.

-The animate function is used to apply the custom animation effect to elements.

-Syntax:

$(selector).animate({params}, [duration], [easing], [callback])

“param” defines the CSS properties on which you want to apply the animation.

“duration” specify how long the animation will run. It can be one of following values : “slow”, “fast”, “normal” or milliseconds

“easing” is the string which specify the function for the transition.

“callback” is the function which we want to run once the animation effect is complete.

For example

Click Me

</div>

</div>

Following is the jQuery to animate opacity, left offset, and height of the mydiv element

$('# clickToAnimate’).click(function() {

$('#book').animate({

opacity: 0.30,

left: '+=20',

height: 'toggle'

}, 3000, function() {

// run after the animation complete.

});

Q101. What is .siblings() method in jQuery?

When we want to fetch siblings of every elements in the set of matched elements then we can use siblings() method.

We filter the elements fetched by an optional selector.

Syntax : .siblings( [selector])

“selector” is the selector expression which specify the matched elements.

For example

<ul>

</ul>

Now we want to find the siblings of the element of id “second_item” and change the text color to Blue :

$(‘li.second_item’).siblings().css(‘color’,’blue’);

If we want specific sibling elements for example the elements having class “myitem” then we can pass a optional selector:

$(‘li.second_item’).siblings(‘.myitem’).css(‘color’,’blue’);

Q102. Explain width() vs css(‘width’).

In jQuery, there are two way to change the width of an element.

One way is using .css(‘width’) and other way is using .width().

For example

$(‘#mydiv’).css(‘width’,’300px’);

$(‘#mydiv’).width(100);

The difference in .css(‘width’) and .width() is the data type of value we specify or return from the both functions.

In .css(‘width’) we have to add “px” in the width value while in .width() we don’t have to add.

When you want to get the width of “mydiv” element then .css(‘width’) will return ‘300px’ while .width() will return only integer value 300.

Q103. What is the use of jQuery.data()?

jQuery.data() is used to set/return arbitrary data to/from an element.

Syntax: jQuery.data(element, key, value)

“element” is the DOM element to which the data is associated.

“key” is an arbitrary name of the piece of data.

“value” is value of the specified key.

Suppose we want to set the data for a span element:

jQuery.data(span, “item”, { val1: 10, val2: "myitem" });

If we want to retrieve the data related to div element and set it to label’s data:

$("label:val1").text(jQuery.data(div, "item").val1);

$("label:val2").text(jQuery.data(div, "item").val2);

Q104. Explain bind() vs live() vs delegate() methods.

-The bind() method will not attach events to those elements which are added after DOM is loaded while live() and delegate() methods attach events to the future elements also.

-The difference between live() and delegate() methods is live() function will not work in chaining. It will work only on an selector or an element while delegate() method can work in chaining.

For example

$(document).ready(function(){

$("#myTable").find("tr").live("click",function(){

alert($(this).text());

});

Above code will not work using live() method. But using delegate() method we can accomplish this.

$(document).ready(function(){

$("#dvContainer")children("table").delegate("tr","click",function(){

alert($(this).text());

});

Q105. Explain the each() function.

-The each() function specify the function to be called for every matched element.

Syntax:

$(selector).each(function (index, element))

“index” is the index position of the selector.

“selector” specifies the current selector where we can use “this” selector also.

In the case when we need to stop the each loop early then we can use “return false;”

For example

$("#clickme").click(function(){

$("li").each(function(){

document.write($(this).text())

});

This will write the text for each “li” element.

Q106. Explain slideToggle() effect.

-slideToggle() effect is used to give animated sliding effect to an element.

Syntax:

slideToggle([ duration] [, easing] [, callback])

“duration” is the number specifying how long the animation will run.

“easing” is the string which specify the function for the transition.

“callback” is the function which we want to run once the animation is complete.

If the element is visible then this effect will slide the element up side and make it completely hidden. If the element is hidden then slideToggle() effect will slide it down side and make it visible.

We can specify the toggle speed with this effect.

For example

$("#clickme").click(function(){

$("#mydiv").slideToggle(“slow”, function(){

//run after the animation is complete.

});

Q107. What is difference between $(this) and ‘this’ in jQuery?

Refer the following example

$(document).ready(function(){

$(‘#clickme’).click(function(){

alert($(this).text());

alert(this.innerText);

});

-this and $(this) references the same element but the difference is that “this” is used in traditional way but when “this” is used with $() then it becomes a jQuery object on which we can use the functions of jQuery.

-In the example given, when only “this” keyword is used then we can use the jQuery text() function to get the text of the element, because it is not jQuery object. Once the “this” keyword is wrapped in $() then we can use the jQuery function text() to get the text of the element.

Q108. What is the use of param() method.

The param() method is used to represent an array or an object in serialize manner.

While making an ajax request we can use these serialize values in the query strings of URL.

Syntax: $.param(object | array, boolValue)

“object | array” specifies an array or an object to be serialized.

“boolValue” specifies whether to use the traditional style of param serialization or not.

For example:

personObj=new Object();

empObject.name="Arpit";

empObject.age="24";

empObject.dept=”IT”;

$("#clickme").click(function(){

$("span").text($.param(empObject));

});

It will set the text of span to “name=Arpit&age=24&dep=IT”

Q109. What is jQuery.holdReady() function?

-By using jQuery.holdReady() function we can hold or release the execution of jQuery’s ready event.

-This method should be call before we run ready event.

-To delay the ready event, we have to call

jQuery.holdReady(true);

-When we want to release the ready event then we have to call

jQuery.holdReady(false);

-This function is helpful when we want to load any jQuery plugins before the execution of ready event.

For example

$.holdReady(true);

$.getScript("xyzplugin.js", function() {

$.holdReady(false);

});

Q110. Explain .empty() vs .remove() vs .detach().

-.empty() method is used to remove all the child elements from matched elements.

-.remove() method is used to remove all the matched element. This method will remove all the jQuery data associated with the matched element.

-.detach() method is same as .remove() method except that the .detach() method doesn’t remove jQuery data associated with the matched elements.

-.remove() is faster than .empty() or .detach() method.

Syntax:

$(selector).empty();

$(selector).remove();

$(selector).detach();

Q111. How to read, write and delete cookies in jQuery?

-To deal with cookies in jQuery we have to use the Dough cookie plugin.

-Dough is easy to use and having powerful features.

-Create cookie

$.dough("cookie_name", "cookie_value");

Read Cookie

$.dough("cookie_name");

Delete cookie

$.dough("cookie_name", "remove");

Q112. Is window.onload is different from document.ready()?

- The window.onload() is Java script function and document.ready() is jQuery event which are called when page is loaded.

- The difference is that document.ready() is called after the DOM is loaded without waiting for all the contents to get loaded. While window.onload() function waits until the contents of page is loaded.

- Suppose there is very large image on a page, at that time window.onload() will wait until that image is loaded totally.

- So while using the window.onlaod() function the execution will be slow, but the document.ready() will not wait until the image is loaded.

Q113. What is Chaining in jQuery?

- Chaining is very powerful feature of jQuery.

- Chaining means specifying multiple function and/or selectors to an element.

- Examine the below example

$(document).ready(function(){

$('#mydiv').css('color', 'blue');

$('#mydiv').addClass('myclass');

$('#mydiv').fadeIn('fast');

}

By using chaining we can write above code as follows

$(document).ready(function(){

$('#mydiv').css('color', 'blue').addClass('myclass').fadeIn('fast');

});

-Advantage of chaining is that it makes your code simple and simple to manage.

-The execution becomes faster because the code search for the element only once.

Q114. What is difference between sorting string array and sorting numerical array in jQuery?

The sort method is used to sort any array elements. It sorts the string elements alphabetically.

For example

$(document).ready(function(){

var mylist = [ “Apple”,”Orange”,”Banana”];

mylist = mylist.sort();

$(“#mydiv”).html(list.join(“”));

});

It will give following output

Apple

Banana

Orange

Now we declare a numerical array and use sort() method to sort its elements.

$(document).ready(function(){

var mylist = [ “20”,”3””100”,”50”];

mylist = mylist.sort();

$(“#mydiv”).html(list.join(“”));

});

It will give following output

100

Q115. What is difference between prop and attr?

In jQuery both prop() and attr() function is used to set/get the value of specified property of an element.

The difference in both the function is that attr() returns the default value of the property while the prop() returns the current value of the property.

For example

$('input').prop('value', 'Changed Value');

-.attr('value') will return 'My Value'

-.prop('value') will return 'Changed Value'

Q116. How to always reference latest version of jQuery?

When you reference the jQuery on your web page, you have to specify the version number also.

src=”http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js”>

</script>

Above code will always load the 1.5.1 version of jQuery. If you reference the latest jQuery then you don’t need to change the code every time the new version of jQuery is released.

To achieve this you have to use following code

src=”http://code.jquery.com/jquery-latest.min.js”>

</script>

This code will always reference the latest version of jQuery in your page.

Q117. What is resize() function in jQuery?

The resize() function is called whenever the browser size is changed. This event can be only used with $(window).

Syntax:

.resize([event_data], handler(event_object))

-The “event_data” is the data to be sent to the handler.

-The “handler(event_object)” is a function to be called each time when the window is resized.

For example

$(window).resize(function() {

$('#message).text('window is resized to ' + $(window).width() + ‘x’ + $(window).height());

});

What is the difference between Body.OnLoad and jQuery document.ready() Event?

Both Body.OnLoad() event and jQuery.ready() event will execute the javascript code when the page is loaded.

The main differences between the two are:

Body.Onload() event will be called only after the DOM and associated resources like images got loaded, but jQuery's document.ready() event will be called once the DOM is loaded i.e., it wont wait for the resources like images to get loaded. Hence, the functions in jQuery's ready event will get executed once the HTML structure is loaded without waiting for the resources.
We can have multiple document.ready() in a page but Body.Onload() event cannot.

Defining Body.Onload() event<body onload="javascript function name or the atcual script">

Defining jQuery.ready() event

</script>

Q.How check currently loaded jQuery UI version on the page?
Ans: // Returns jQuery UI version (ex: 1.8.2) or undefined
$.ui.version

Q. What is jQuery.noConflict?

Ans: As other client side libraries like MooTools, Prototype can be used with jQuery and they also use $() as their global function and to define variables. This situation creates conflict as $() is used by jQuery and other library as their global function. To overcome from such situations, jQuery has introduced jQuery.noConflict().

jQuery.noConflict();

// Use jQuery via jQuery(...)

jQuery(document).ready(function(){

jQuery("div").hide();

});

You can also use your own specific character in the place of $ sign in jQuery.

var $j = jQuery.noConflict();

// Use jQuery via jQuery(...)

$j(document).ready(function(){

$j("div").hide();

});

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

Ans: 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 bodyonload 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.

Q. What is the difference between .js and .min.js?

Ans: jQuery library comes in 2 different versions Production and Deployment. The deployment version is also known as minified version. So .min.js is basically the minified version of jQuery library file. Both the files are same as far as functionality is concerned. but .min.js is quite small in size so it loads quickly and saves bandwidth.

Q. Why there are two different version of jQuery library?

Ans: jQuery library comes in 2 different versions.

1. Production

2. Deployment

The production version is quite useful at development time as jQuery is open source and if you want to change something then you can make those changes in production version. But the deployment version is minified version or compressed version so it is impossible to make changes in it. Because it is compressed, so its size is very less than the production version which affects the page load time.

Q. What is a CDN?

Ans: A content delivery network or content distribution network (CDN) is a large distributed system of servers deployed in multiple data centers across the Internet. The goal of a CDN is to serve content to end-users with high availability and high performance.

Q. Which are the popular jQuery CDN? and what is the advantage of using CDN?

Ans: There are 3 popular jQuery CDNs.

1. 1. Google.

2. 2. Microsoft

3. 3. jQuery.

Advantage of using CDN.

· It reduces the load from your server.

· It saves bandwidth. jQuery framework will load faster from these CDN.

· The most important benefit is it will be cached, if the user has visited any site which is using jQuery framework from any of these CDN

Q. How to load jQuery from CDN?

Ans: Below is the code to load jQuery from all 3 CDNs.
Code to load jQuery Framework from Google CDN

src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">

</script>

Code to load jQuery Framework from Microsoft CDN

src="http://ajax.microsoft.com/ajax/jquery/jquery-1.9.1.min.js">

</script>

Code to load jQuery Framework from jQuery Site(EdgeCast CDN)

src="http://code.jquery.com/jquery-1.9.1.min.js">

</script>

Q. How to load jQuery locally when CDN fails?

Ans: It is a good approach to always use CDN but sometimes what if the CDN is down (rare possibility though) but you never know in this world as anything can happen.

Below given jQuery code checks whether jQuery is loaded from Google CDN or not, if not then it references the jQuery.js file from your folder.

if (typeof jQuery == 'undefined')

{

document.write(unescape("%3Cscript src='Scripts/jquery.1.9.1.min.js' type='text/javascript'%3E%3C/script%3E"));

}

</script>

It first loads the jQuery from Google CDN and then check the jQuery object. If jQuery is not loaded successfully then it will references the jQuery.js file from hard drive location. In this example, the jQuery.js is loaded from Scripts folder.

Q. What are selectors in jQuery and how many types of selectors are there?

Ans: 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.

Q.What are the fastest selectors in Jquery?
Ans: ID and element selectors are the fastest selectors

Q.What are the slower selecoters in Jquery?
Ans: Class selectors are slower

Q.Which one is faster Jquery ID selector or JavaScript getElementById()?
(Jquery ID selector vs JavaScript getElementById())
Ans: JavaScript getElementById() is faster than Jquery Id ($("#elementID")) selector

Q.Where Jquery code execute? On client browser or server browser?
On client browser

Q.What is Chaining in jQuery?
Ans:
In jQuery, Chaining means to connect multiple functions, events on selectors. look at Sample Code 1 and 2.

Q.What are features of JQuery
or
What can be done using JQuery?
Features of Jquery
1. One can easily provide effects and can do animations.
2. Applying / Changing CSS.
3. Cool plugins.
4. Ajax support
5. DOM selection events
6. Event Handling

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

Ans: Native JavaScipt is always fast. jQuery method to select txtName "$('#txtName')" will internally makes a call todocument.getElementByID('txtName'). As jQuery is written on top of JavaScript and it internally uses JavaScript only So JavaScript is always fast.

Q. Difference between $(this) and 'this' in jQuery?

Ans: this and $(this) refers to the same element. The only difference is the way they are used. 'this' is used in traditional sense, when 'this' is wrapped in $() then it becomes a jQuery object and you are able to use the power of jQuery.

$(document).ready(function(){

$('#spnValue').mouseover(function(){

alert($(this).text());

});

In below example, this is an object but since it is not wrapped in $(), we can't use jQuery method and use the native JavaScript to get the value of span element.

$(document).ready(function(){

$('#spnValue').mouseover(function(){

alert(this.innerText);

});

});

Q. What is asynchronous in Jquery ?

A. By default, all requests are sent asynchronously (i.e. this is set to true by default). If you need synchronous requests, set this option to false.

contentType (default: 'application/x-www-form-urlencoded; charset=UTF-8')

crossDomain (default: false for same-domain requests, true for cross-domain requests)



$.ajax({



  url: "data.php",



  context: document.body



}).done(function() {



  $( this ).addClass( "content" );



});

Q. What is Proxy in jquery?A. Proxy is an object that can be used to control and access to another object. It implements the same interface as this other object and passes on any method invocations to it. This other object is often called the real subject. one way to combine that is to implement a proxy pattern in JavaScript, enabling the basics of aspect-oriented programming (AOP)




(function() {




  // log all calls to setArray



  var proxied = jQuery.fn.setArray;



  jQuery.fn.setArray = function() {



    console.log( this, arguments );



    return proxied.apply( this, arguments );



  };



})();
Q.What is Closure?A. Closures are created whenever a variable that is defined outside the current scope is accessed from within some inner scope. In the following example, the variable counter is visible within the create, increment, and print functions, but not outside of them.




function create() {




  var counter = 0;



  return {



    increment: function() {



      counter++;



    },



    print: function() {



      console.log( counter );



    }



  }



}



var c = create();



c.increment();



c.print(); // 1

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Saturday, August 16, 2014

Jquery Questions and Answers

What is the difference between Body.OnLoad and jQuery document.ready() Event?

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