Q1. What is jQuery?
Ans:
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 library and as per a survey
it runs on every second website.
Q2. Why do we use jQuery?
Ø Ans: Due to following
advantages.
Ø Easy to use and learn.
Ø Easily expandable.
Ø Cross-browser support (IE 6.0+, FF 1.5+,
Safari 2.0+, Opera 9.0+)
Ø Easy to use for DOM manipulation and
traversal.
Ø Large pool of built in methods.
Ø AJAX Capabilities.
Ø Methods for changing or applying CSS, creating
animations.
Ø Event detection and handling.
Ø Tons of plug-ins for all kind of needs.
Q3. How JavaScript and jQuery are different?
Ans:
JavaScript is a language While jQuery is a library built in the JavaScript
language that helps to use the JavaScript language.
Q4. Is jQuery replacement of Java Script?
Ans: 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.
Q5. Is jQuery a library for client scripting
or server scripting?
Ans.
Client side scripting.
Q6. Is jQuery a W3C standard?
Ans:
No. jQuery is not a W3C standard.
Q7. What is the basic need to start with
jQuery?
Ans:
To start with jQuery, one need to make reference of it's library. The latest
version of jQuery can be downloaded from jQuery.com.
Q8. Which is the starting point of code
execution in jQuery?
Ans:
The starting point of jQuery code execution is $(document).ready() function
which is executed when DOM is loaded.
Q9. What does dollar sign ($) means in jQuery?
Ans:
Dollar Sign is nothing but it's an alias for JQuery. Take a look at below
jQuery code.
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$(document).ready(function(){
});
Over
here $ sign can be replaced with "jQuery" keyword.
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jQuery(document).ready(function(){
});
Q10. Can we have multiple document.ready()
function on the same page?
Ans: YES. We can have any number of
document.ready() function on the same page.
Q11. Can we use our own specific character in
the place of $ sign in jQuery?
Ans: Yes. It is possible using
jQuery.noConflict().
Q12. Is it possible to use other client side
libraries like MooTools, Prototype along with jQuery?
Ans: Yes.
Q13. 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().
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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.
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var $j = jQuery.noConflict();
// Use jQuery via jQuery(...)
$j(document).ready(function(){
$j("div").hide();
});
Q14. 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
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.
Q15. What is the difference between .js and
.min.js?
Ans:
jQuery library comes in 2 different versions Development and
Production/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.
Q16. Why there are two different version of
jQuery library?
Ans:
jQuery library comes in 2 different versions.
1. Development
2. Production/Deployment
The
development 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
development 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.
Q17. 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.
Q18. 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.
Ø It reduces the load from your server.
Ø It saves bandwidth. jQuery framework will load
faster from these CDN.
Ø 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
Q19. 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
Code to load jQuery Framework from Google CDN
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<script type="text/javascript"
src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
Code
to load jQuery Framework from Microsoft CDN
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<script type="text/javascript"
src="http://ajax.microsoft.com/ajax/jquery/jquery-1.9.1.min.js">
</script>
Code
to load jQuery Framework from jQuery Site(EdgeCast CDN)
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<script type="text/javascript"
src="http://code.jquery.com/jquery-1.9.1.min.js">
</script>
Q20. 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.
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.
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<script type="text/javascript">
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.
Q21. 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.
Q22. How do you select element by ID in
jQuery?
Ans:
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,
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$('#txtName')
Q23. What does $("div") will select?
Ans:
This will select all the div elements on page.
Q24. How to select element having a particular
class (".selected")?
Ans: $('.selected'). This selector is known as
class selector. We need to prefix the class name with "." (dot).
Q25. What does $("div.parent") will
select?
Ans:
All the div element with parent class.
Q26. What are the fastest selectors in jQuery?
Ans:
ID and element selectors are the fastest selectors in jQuery.
Q27. What are the slow selectors in jQuery?
Ans:
class selectors are the slow compare to ID and element.
Q28. How jQuery selectors are executed?
Ans:
Your last selectors is always executed first. For example, in below jQuery
code, jQuery will first find all the elements with class ".myCssClass" and after that it will
reject all the other elements which are not in "p#elmID".
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$("p#elmID
.myCssClass");
Q29. 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 to document.getElementByID('txtName'). As jQuery is written on top
of JavaScript and it internally uses JavaScript only So JavaScript is always
fast.
Q30. 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 $() then
it becomes a jQuery object and you are able to use the power of jQuery.
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$(document).ready(function(){
$('#spnValue').mouseover(function(){
alert($(this).text());
});
});
In
below example, this is an object but since it is not wrapped in $(), we can't use jQuery method
and use the native JavaScript to get the value of span element.
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$(document).ready(function(){
$('#spnValue').mouseover(function(){
alert(this.innerText);
});
});
Q31. How do you check if an element is empty?
Ans:
There are 2 ways to check if element is empty or not. We can check using
":empty" selector.
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$(document).ready(function(){
if ($('#element').is(':empty')){
//Element is empty
}
});
And
the second way is using the "$.trim()" method.
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$(document).ready(function(){
if($.trim($('#element').html())=='') {
//Element is empty
}
});
Q32. How do you check if an element exists or
not in jQuery?
Ans:
Using jQuery length property, we can ensure whether element exists or not.
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$(document).ready(function(){
if ($('#element').length > 0){
//Element exists
}
});
Q33. What is the use of jquery .each()
function?
Ans:
The $.each() function is used to iterate
over a jQuery object. The $.each() function can be used to
iterate over any collection, whether it is an object or an array.
Q34. What is the difference between
jquery.size() and jquery.length?
Ans:
jQuery .size() method returns number of
element in the object. But it is not preferred to use the size()method as jQuery provide .length property and which does the
same thing. But the .length property is preferred because
it does not have the overhead of a function call.
Q35. What is the difference between $('div')
and $('<div/>') in jQuery?
Ans:
$('<div/>') : This creates a new div element. However this is not added
to DOM tree unless you don't append it to any DOM element.
$('div') : This selects all the div element present on the page.
$('div') : This selects all the div element present on the page.
Q36. What is the difference between parent()
and parents() methods in jQuery?
Ans:
The basic difference is the parent() function travels only one
level in the DOM tree, where parents() function search through the whole DOM
tree.
Q37. What is the difference between eq() and
get() methods in jQuery?
Ans: eq() returns the element as a
jQuery object. This method constructs a new jQuery object from one element
within that set and returns it. That means that you can use jQuery functions on
it.
get() return a DOM element. The method retrieve the DOM elements matched by the jQuery object. But as it is a DOM element and it is not a jQuery-wrapped object. So jQuery functions can't be used.
get() return a DOM element. The method retrieve the DOM elements matched by the jQuery object. But as it is a DOM element and it is not a jQuery-wrapped object. So jQuery functions can't be used.
Q38. How do you implement animation
functionality?
Ans:
The .animate() method allows us to create animation effects on any numeric CSS
property. This method changes an element from one state to another with CSS
styles. The CSS property value is changed gradually, to create an animated
effect.
Syntax is:
Syntax is:
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(selector).animate({styles},speed,easing,callback)
Ø styles: Specifies one or more CSS
properties/values to animate.
Ø duration: Optional. Specifies the speed of the
animation.
Ø easing: Optional. Specifies the speed of the
element in different points of the animation. Default value is
"swing".
Ø callback: Optional. A function to be executed
after the animation completes.
Ø Simple use of animate
function is,
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$("btnClick").click(function(){
$("#dvBox").animate({height:"100px"});
});
Q39. How to disable jQuery animation?
Ans:
Using jQuery property "jQuery.fx.off", which when set to true, disables all
the jQuery animation. When this is done, all animation methods will immediately
set elements to their final state when called, rather than displaying an
effect.
Q40. How do you stop the currently-running
animation?
Ans:
Using jQuery ".stop()" method.
Q41. What is the difference between .empty(),
.remove() and .detach() methods in jQuery?
Ans:
All these methods .empty(), .remove() and .detach() are used for removing
elements from DOM but they all are different.
.empty(): This method removes all the child element of the matched element where remove() method removes set of matched elements from DOM.
.remove(): Use .remove() when you want to remove the element itself, as well as everything inside it. In addition to the elements themselves, all bound events and jQuery data associated with the elements are removed.
.detach(): This method is the same as .remove(), except that .detach() keeps all jQuery data associated with the removed elements. This method is useful when removed elements are to be reinserted into the DOM at a later time.
.empty(): This method removes all the child element of the matched element where remove() method removes set of matched elements from DOM.
.remove(): Use .remove() when you want to remove the element itself, as well as everything inside it. In addition to the elements themselves, all bound events and jQuery data associated with the elements are removed.
.detach(): This method is the same as .remove(), except that .detach() keeps all jQuery data associated with the removed elements. This method is useful when removed elements are to be reinserted into the DOM at a later time.
Q42. Explain .bind() vs .live() vs .delegate()
vs .on()
Ans:
All these 4 jQuery methods are used for attaching events to selectors or
elements. But they all are different from each other.
<a href="http://jquerybyexample.blogspot.com/2010/06/jquery-bind-function-exampledemo.html">.bind()</a>: This is the easiest and quick method to bind events. But the issue with bind() is that it doesn't work for elements added dynamically that matches the same selector. bind() only attach events to the current elements not future element. Above that it also has performance issues when dealing with a large selection.
<a href="http://jquerybyexample.blogspot.com/2010/06/jquery-live-function-exampledemo.html">.live()</a>: This method overcomes the disadvantage of bind(). It works for dynamically added elements or future elements. Because of its poor performance on large pages, this method is deprecated as of jQuery 1.7 and you should stop using it. Chaining is not properly supported using this method.
<a href="http://jquerybyexample.blogspot.com/2010/08/jquery-delegate-function-exampledemo.html">.delegate()</a>: The .delegate() method behaves in a similar fashion to the .live() method, but instead of attaching the selector/event information to the document, you can choose where it is anchored and it also supports chaining.
.on(): Since live was deprecated with 1.7, so new method was introduced named ".on()". This method provides all the goodness of previous 3 methods and it brings uniformity for attaching event handlers.
<a href="http://jquerybyexample.blogspot.com/2010/06/jquery-bind-function-exampledemo.html">.bind()</a>: This is the easiest and quick method to bind events. But the issue with bind() is that it doesn't work for elements added dynamically that matches the same selector. bind() only attach events to the current elements not future element. Above that it also has performance issues when dealing with a large selection.
<a href="http://jquerybyexample.blogspot.com/2010/06/jquery-live-function-exampledemo.html">.live()</a>: This method overcomes the disadvantage of bind(). It works for dynamically added elements or future elements. Because of its poor performance on large pages, this method is deprecated as of jQuery 1.7 and you should stop using it. Chaining is not properly supported using this method.
<a href="http://jquerybyexample.blogspot.com/2010/08/jquery-delegate-function-exampledemo.html">.delegate()</a>: The .delegate() method behaves in a similar fashion to the .live() method, but instead of attaching the selector/event information to the document, you can choose where it is anchored and it also supports chaining.
.on(): Since live was deprecated with 1.7, so new method was introduced named ".on()". This method provides all the goodness of previous 3 methods and it brings uniformity for attaching event handlers.
Q43. What is wrong with this code line
"$('#myid.3').text('blah blah!!!');"
Ans:
The problem with above statement is that the selectors is having meta
characters and to use any of the meta-characters ( such as
!"#$%&'()*+,./:;<=>?@[\]^`{|}~ ) as a literal part of a name, it
must be escaped with with two backslashes: \\. For example, an element with
id="foo.bar", can use the selector $("#foo\\.bar").
So the correct syntax is,
So the correct syntax is,
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$('#myid\\.3').text('blah
blah!!!');
Q44. How to create clone of any object using
jQuery?
Ans:
jQuery provides clone() method which performs a deep
copy of the set of matched elements, meaning that it copies the matched
elements as well as all of their descendant elements and text nodes.
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$(document).ready(function(){
$('#btnClone').click(function(){
$('#dvText').clone().appendTo('body');
return false;
});
});
Q45. Does events are also copied when you
clone any element in jQuery?
Ans:
As explained in previous question, using clone() method,
we can create clone of any element but the default implementation of the clone() method doesn't copy events
unless you tell the clone() method to copy the events.
The clone() method takes a parameter, if
you pass true then it will copy the events as well.
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$(document).ready(function(){
$("#btnClone").bind('click', function(){
$('#dvClickme').clone(true).appendTo('body');
});
Q46. What is difference between prop and attr?
Ans: attr(): Get the value of an
attribute for the first element in the set of matched elements. Whereas,.prop(): (Introduced in jQuery 1.6)
Get the value of a property for the first element in the set of matched
elements.
Attributes carry additional information about an HTML element and come in name="value" pairs. Where Property is a representation of an attribute in the HTML DOM tree. once the browser parse your HTML code ,corresponding DOM node will be created which is an object thus having properties.
attr() gives you the value of element as it was defines in the html on page load. It is always recommended to use prop() to get values of elements which is modified via javascript/jquery , as it gives you the original value of an element's current state.
Attributes carry additional information about an HTML element and come in name="value" pairs. Where Property is a representation of an attribute in the HTML DOM tree. once the browser parse your HTML code ,corresponding DOM node will be created which is an object thus having properties.
attr() gives you the value of element as it was defines in the html on page load. It is always recommended to use prop() to get values of elements which is modified via javascript/jquery , as it gives you the original value of an element's current state.
Q47. What is event.PreventDefault?
Ans:
The event.preventDefault() method stops the default
action of an element from happening. For example, Prevents a link from
following the URL.
Q48. What is the difference between
event.PreventDefault and event.stopPropagation?
Ans: event.preventDefault(): Stops the default action of
an element from happening.
event.stopPropagation(): Prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event. For example, if there is a link with a click method attached inside of a DIV or FORM that also has a click method attached, it will prevent the DIV or FORM click method from firing.
event.stopPropagation(): Prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event. For example, if there is a link with a click method attached inside of a DIV or FORM that also has a click method attached, it will prevent the DIV or FORM click method from firing.
Q49. What is the difference between
event.PreventDefault and "return false"?
Ans: e.preventDefault() will prevent the default
event from occurring, e.stopPropagation() will prevent the event from
bubbling up and return false will do both.
Q50. What is the difference between
event.stopPropagation and event.stopImmediatePropagation?
Ans: event.stopPropagation() allows other handlers on the
same element to be executed, while event.stopImmediatePropagation() prevents every event from
running. For example, see below jQuery code block.
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$("p").click(function(event){
event.stopImmediatePropagation();
});
$("p").click(function(event){
// This function won't be executed
$(this).css("background-color", "#f00");
});
If event.stopPropagation was used in previous example,
then the next click event on p element which changes the css will fire, but in
case event.stopImmediatePropagation(), the next p click event will
not fire.
Q51. How to check if number is numeric while
using jQuery 1.7+?
Ans:
Using "<a
href="http://jquerybyexample.blogspot.com/2011/11/jqueryisnumeric-in-jquery-17.html">isNumeric()</a>" function which was
introduced with jQuery 1.7.
Q52. How to check data type of any variable in
jQuery?
Q53. How do you attach a event to element
which should be executed only once?
Ans: Using
jQuery one() method. This attaches a
handler to an event for the element. The handler is executed at most once per
element. In simple terms, the attached function will be called only once.
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$(document).ready(function() {
$("#btnDummy").one("click", function() {
alert("This will be displayed only once.");
});
});
Q54. Can you include multiple version of
jQuery? If yes, then how they are executed?
Ans:
Yes. Multiple versions of jQuery can be included in same page.
Q55. In what situation you would use multiple
version of jQuery and how would you include them?
Ans:
Well, it is quite possible that the jQuery plugins which are used are dependent
on older version but for your own jQuery code, you would like to use newer
version. So because of this dependency, multiple version of jQuery may required
sometimes on single page.
Below code shows how to include multiple version of jQuery.
Below code shows how to include multiple version of jQuery.
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<script type='text/javascript'
src='js/jquery_1.9.1.min.js'></script>
<script type='text/javascript'>
var $jq =
jQuery.noConflict();
</script
By
this way, for your own jQuery code use "$jq", instead of
"$" as "$jq" refers to jQuery 1.9.1, where "$"
refers to 1.7.2.
Q56. Is it possible to hold or delay
document.ready execution for sometime?
Ans:
Yes, its possible. With Release of jQuery 1.6, a new method "jQuery.holdReady(hold)" was introduced. This
method allows to delay the execution of document.ready() event. document.ready() event is called as soon as
your DOM is ready but sometimes there is a situation when you want to load
additional JavaScript or some plugins which you have referenced.
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$.holdReady(true);
$.getScript("myplugin.js", function() {
$.holdReady(false);
});
Q57. What is chaining in jQuery?
Ans:
Chaining is one of the most powerful feature of jQuery. In jQuery, Chaining
means to connect multiple functions, events on selectors. It makes your code
short and easy to manage and it gives better performance. The chain starts from
left to right. So left most will be called first and so on.
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$(document).ready(function(){
$('#dvContent').addClass('dummy');
$('#dvContent').css('color', 'red');
$('#dvContent').fadeIn('slow');
});
The
above jQuery code sample can be re-written using chaining. See below.
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$(document).ready(function(){
$('#dvContent').addClass('dummy')
.css('color', 'red')
.fadeIn('slow');
});
Not
only functions or methods, chaining also works with events in jQuery.
Q58. How does caching helps and how to use
caching in jQuery?
Ans:
Caching is an area which can give you awesome performance, if used properly and
at the right place. While using jQuery, you should also think about caching.
For example, if you are using any element in jQuery more than one time, then
you must cache it. See below code.
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$("#myID").css("color", "red");
//Doing some other stuff......
$("#myID").text("Error occurred!");
Now
in above jQuery code, the element with #myID is
used twice but without caching. So both the times jQuery had to traverse
through DOM and get the element. But if you have saved this in a variable then
you just need to reference the variable. So the better way would be,
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var $myElement = $("#myID").css("color", "red");
//Doing some other stuff......
$myElement.text("Error occurred!");
So
now in this case, jQuery won't need to traverse through the whole DOM tree when
it is used second time. So in jQuery, Caching is like saving the jQuery
selector in a variable. And using the variable reference when required instead
of searching through DOM again.
Q59. You get "jquery is not defined"
or "$ is not defined" error. What could be the reason?
Ans:
There could be many reasons for this.
·
You have forgot to
include the reference of jQuery library and trying to access jQuery.
·
You have include the
reference of the jQuery file, but it is after your jQuery code.
·
The order of the
scripts is not correct. For example, if you are using any jQuery plugin and you
have placed the reference of the plugin js before the jQuery library then you
will face this error.
Q60. How to write browser specific code using
jQuery?
Ans:
Using jQuery.browser property, we can write browser specific code. This
property contains flags for the useragent, read from navigator.userAgent. This
property was removed in jQuery 1.9.
Q61. Can we use jQuery to make ajax request?
Ans:
Yes. jQuery can be used for making ajax request.
Q62. What are various methods to make ajax
request in jQuery?
Ans:
Using below jQuery methods, you can make ajax calls.
Ø load() : Load a piece of html into a container DOM
Ø $.getJSON(): Load JSON with GET method.
Ø $.getScript(): Load a JavaScript file.
Ø $.get(): Use to make a GET call and play extensively
with the response.
Ø $.post(): Use to make a POST call and don't want to
load the response to some container DOM.
Ø $.ajax(): Use this to do something on XHR failures, or
to specify ajax options (e.g. cache: true) on the fly.
Q63. Is there any advantage of using $.ajax()
for ajax call against $.get() or $.post()?
Ans:
By using jQuery post()/ jQuery get(), you always trust the
response from the server and you believe it is going to be successful all the
time. Well, it is certainly not a good idea to trust the response. As there can
be n number of reason which may lead to failure of response.
Where jQuery.ajax() is jQuery's low-level AJAX implementation. $.get and $.post are higher-level abstractions that are often easier to understand and use, but don't offer as much functionality (such as error callbacks). more here.
Where jQuery.ajax() is jQuery's low-level AJAX implementation. $.get and $.post are higher-level abstractions that are often easier to understand and use, but don't offer as much functionality (such as error callbacks). more here.
Q64. What are deferred and promise object in
jQuery?
Ans:
Deferred and promise are part of jQuery since version 1.5 and they help in
handling asynchronous functions like Ajax.
Q65. Can we execute/run multiple Ajax request
simultaneously in jQuery? If yes, then how?
Ans:
Yes, it is possible to execute multiple Ajax request simultaneously or in
parallel. Instead of waiting for first ajax request to complete and then issue
the second request is time consuming. The better approach to speed up things
would be to execute multiple ajax request simultaneously.
Using jQuery .when() method which provides a way to execute callback functions based on one or more objects, usually Deferred objects that represent asynchronous events. more here.
Using jQuery .when() method which provides a way to execute callback functions based on one or more objects, usually Deferred objects that represent asynchronous events. more here.
Q66. Can you call C# code-behind method using
jQuery? If yes,then how?
Ans:
Yes. We can call C# code-behind function via $.ajax. But for do that it is
compulsory to mark the method as WebMethod.
Q67. Which is the latest version of jQuery
library?
Ans:
The latest version (when this post is written) of jQuery is 1.10.2 or 2.0.3.
jQuery 2.x has the same API as jQuery 1.x, but does not support Internet
Explorer 6, 7, or 8.
Q68. Does jQuery 2.0 supports IE?
Ans:
No. jQuery 2.0 has no support for IE 6, IE 7 and IE 8.
Q69. What are source maps in jQuery?
Ans:
In case of jQuery, Source Map is nothing but mapping of minified version of
jQuery against the un-minified version. Source map allows to debug minified
version of jQuery library. Source map feature was release with jQuery 1.9. more here.
Q70. How to use migrate jQuery plugin?
Ans:
with release of 1.9 version of jQuery, many deprecated methods were discarded
and they are no longer available. But there are many sites in production which
are still using these deprecated features and it's not possible to replace them
overnight. So jQuery team provided with jQuery Migrate plugin that makes code
written prior to 1.9 work with it.
So to use old/deprecated features, all you need to do is to provide reference of jQuery Migrate Plugin.
So to use old/deprecated features, all you need to do is to provide reference of jQuery Migrate Plugin.
Q71. Is it possible to get value of multiple
CSS properties in single statement?
Ans:
Well, before jQuery 1.9 release it was not possible but one of the new feature
of jQuery 1.9 was .css()multi-property getter.
Hide Copy Code
var propCollection = $("#dvBox").css([ "width", "height", "backgroundColor" ]);
In
this case, the propCollection will be an array and it will
look something like this.
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{
width: "100px",
height: "200px",
backgroundColor: "#FF00FF"
}
Q72. How do you stop the currently-running
animation, remove all queued animations, and complete all animations for the
matched elements?
Ans:
It can be done via calling .stop([clearQueue
] [, jumpToEnd ]) method
and by passing both the parameters as true.
Q73. What is finish method in jQuery?
Ans:
The .finish() method stops all queued animations and places the element(s) in
their final state. This method was introduced in jQuery 1.9.
Q74. What is the difference between calling
stop(true,true) and finish method?
Ans:
The .finish() method is similar to .stop(true, true) in that it clears the
queue and the current animation jumps to its end value. It differs, however, in
that .finish() also causes the CSS property of all queued animations to jump to
their end values, as well.
Q75. Consider a scenario where things can be
done easily with javascript, would you still prefer jQuery?
Ans:
No. If things can be done easily via CSS or JavaScript then You should not
think about jQuery. Remember, jQuery library always comes with xx kilobyte size
and there is no point of wasting bandwidth.
Q76. Can we use protocol less URL while
referencing jQuery from CDNs?
Ans:
Yes. Below code is completely valid.
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<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
Q77. What is the advantage of using protocol
less URL while referencing jQuery from CDNs?
Ans:
It is quite useful when you are moving from HTTP to HTTPS url. You need to make
sure that correct protocol is used for referencing jQuery library as pages
served via SSL should contain no references to content served through
unencrypted connections.
"protocol-less" URL is the best way to reference third party content that’s available via both HTTP and HTTPS. When a URL’s protocol is omitted, the browser uses the underlying document’s protocol instead.
"protocol-less" URL is the best way to reference third party content that’s available via both HTTP and HTTPS. When a URL’s protocol is omitted, the browser uses the underlying document’s protocol instead.
Q78. What is jQuery plugin and what is the
advantage of using plugin?
Ans:
A plug-in is piece of code written in a standard JavaScript file. These files
provide useful jQuery methods which can be used along with jQuery library
methods. jQuery plugins are quite useful as its piece of code which is already
written by someone and re-usable, which saves your development time.
Q79. What is jQuery UI?
Ans:
jQuery UI is a curated set of user interface interactions, effects, widgets,
and themes built on top of the jQuery JavaScript Library that can be used to
build interactive web applications.
Q80. What is the difference between jQuery and
jQuery UI?
Ans:
jQuery is the core library. jQueryUI is built on top of it. If you use
jQueryUI, you must also include jQuery.
