Fresh JQuery Developer Interview Questions & Answers:

1. Can you please explain the difference between jQuery's ready and holdReady?

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.

2. When can JQuery be used?

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())

3. If you have a server control(asp.net server control, Button) and on the click of button you want to call a jquery function, So tell me how you will call a jquery function without postback?

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" />

4. Why we need jQuery?

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

5. What methods used to provide effects in JQuery?

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

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

7. Can you please explain the difference between onload() and document.ready() function used in jQuery?

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.

8. How to get 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);
}
});

9. How you debug Jquery code/ debug jquery?

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.

10. What is the use of .Size() method in Jquery?

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