JQuery Developer Interview Questions & Answers

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jQuery's ready is an event which gets triggered automatically when DOM is ready while holdReady is a signal/flag to hold this triggering. holdReady was included in 1.6 version and it works only if used before the execution/triggering of ready event. Once ready event is fired, it has nothing to do. It is useful in dynamically loading scripts before the ready starts. It release ready event execution when used with a true parameter.

JQuery can be used to perform:
1) Call methods on specific events
2) Traverse the documents
3) For apply CSS
4) Manipulation purpose and
5) To add effects too.
6) For apply animations
7) For give atractive look (dialogbox etc)
8) For asynchronous calls ($.ajax())

ASP.NET provides the OnClientClick property to handle button clicks. You can use this property on Button, LinkButton and ImageButton. The same OnClientClick property also allows you to cancel a postback.
So I can use OnClientClick property and Jquery function will return false.

Example:
Code:
<script type="text/javascript">
function callMe()
{
alert('Hello');
return false;
}
</script>
<asp:Button ID="Button1" runat="server" OnClientClick="return callMe();" Text="Button" />

jQuery is needed for:
★ Used to develop browser compatible web applications.
★ Improve the performance of an application.
★ Very fast and extensible.
★ UI related functions are written in minimal lines of codes

Some effects methods are:
★ FadeIn()
★ FadeOut()
★ Show()
★ Hide()
★ Toggle()

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:
<script type="text/javascript" src="jQuery-1.4.1-min.js"></script>

We can add more than one document.ready() function in a page.
we can have only one onload function.
Document.ready() function is called as soon as DOM is loaded.
body.onload() function is called when everything (DOM, images)gets loaded on the page.

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);
}
});

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.

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

jQuery-x.x.x.js = Pretty and easy to Read this one.
jQuery.x.x.x min.js = Looks like gibberish! But has a smaller file size. Put this one on your site for fast loading and less size.

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.

Basically, the jQuery .each() function is used to loop through each element of the target jQuery object. Very useful for multi element DOM manipulation, looping arrays and object properties.

Example:
In this example alert box will open 3 times because dom contain 3 <li> tags
<script>
$(document).ready(function(){
$("button").click(function(){
$("li").each(function(){
alert($(this).text())
});
});
});
</script>

<ul>
<li>Coffee</li>
<li>Milk</li>
<li>Soda</li>
</ul>

jQuery's data method gives us the ability to associate arbitrary data with DOM nodes and JavaScript objects. This makes our code more concise and clean.

Yes.

Example:
var StateID = $("#StateCbx").val(); // Or you can use it $("#iStateID").val();
var StateName = $("#StateCbx option:selected").text();
alert("Selected combobox text is= " + StateName + " and value is= " + StateID);

Please share your answers.

★ url
★ type
★ data
★ cache
★ beforeSend(xhr)

Specifies data to be sent to the server.

A function to run before the request is sent.

A Boolean value indicating whether the browser should cache the requested pages. Default is true.

Specifies the type of request. (GET or POST).

Specifies the URL to send the request to. Default is the current page.

The Jquery ajax() method is used to perform an AJAX (asynchronous HTTP) request.

We can fire or trigger any click event programmatically by using below methods.

jQuery('#YourElementID').trigger('click');
OR
$('#YourElementID').trigger('click');
OR
jQuery("#YourElementID").click();
OR
$("#YourElementID").click();