JQuery interview questions and Answers Advanced (Multiple Choice)- JQuery Quiz.

In this tutorial, I have selected advanced and basic Jquery Interview questions and answers with examples for freshers and 1 to 3 year experienced candidates.I have also included Objective Jquery ajax interview questions.


Advanced  JQuery interview questions and Answers:

What is Jquery?

jQuery is a JavaScript Library.

Which of the following is correct?

jQuery is a JavaScript Library
jQuery is a JSON Library

Answer :jQuery is a JavaScript Library

jQuery uses CSS selectors and XPath expressions to select elements?

False
True

Answer: True

Which sign does jQuery use as a shortcut for jQuery?

$ sign
% sign
? Sign

Answer: $ sign


Is jQuery a W3C standard?

Yes
No

Answer: NO


$("span"). What does it select?

All span elements
The first span element

Answer: All span elements

Is jQuery a library for client scripting or server scripting?

Client scripting
Server scripting

Answer: Client scripting

Is it possible to use jQuery together with AJAX?

Yes
No

Answer: Yes

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

True
False

Answer :False

jQuery code to set the background color of all span elements to blue?

$("span").style("background-color","blue");
$("span").manipulate("background-color","blue");
$("span").css("background-color","blue");
$("span").layout("background-color","blue");

Answer: $("span").css("background-color","blue");


$("span.intro"). What does it select?

The first span element with class="intro"
The first span element with id="intro"
All span elements with id="intro"
All span elements with class="intro"

Answer: All span elements with class="intro"

jQuery method to hide selected elements?

visible(false)
hidden()
display(none)
hide()

Answer: hide()

jQuery method to set one or more style properties for selected elements?

style()
css()
html()
 
Answer: css()

jQuery method is used to perform an asynchronous HTTP request?

jQuery.ajaxAsync()
jQuery.ajaxSetup()
jQuery.ajax()

Answer: jQuery.ajax()


What scripting language is jQuery written in?

VBScript
C++
JavaScript
C#

Answer: JavaScript

$("div#id1 .cl1"). What does it select?

The first element with id="cl1" inside any div element with class="id1"
All elements with class="cl1" inside the first div element with id="id1"
All div elements with id="id1" or class="cl1"

Answer: All elements with class="cl1" inside the first div element with id="id1"


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.

JQuery Methods used to provide effects?

1. Show()
2. Hide()
3. Toggle()
4. FadeIn()
5. FadeOut()


What are the different type of selectors in Jquery?

1. CSS Selector
2. XPath Selector
3. Custom Selector

What does .size() method of jquery return ?

.size() method of jquery returns number of element in the object.


 How do you get the text value?

$("#textbox1").val();

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

1.$('#num1').attr('checked', true);// Check #num1

2.$('#num1').attr('checked', false);// Uncheck #num1

3.$("#num1").attr('checked', 'checked');// Check #num1

4.$("#num1").removeAttr('checked');// Uncheck #num1


Ajax Request in Jquery

$.ajax({
     url: 'test.php',
     success: function(response) {
        alert(response);
     },
     error: function(res) {
        alert(res.status);
     }
});


Explain the each() function.

$("#num").click(function(){
$("li").each(function(){
document.write($(this).text())
});
});

Object in Object oriented programming

object is an instance of a class.An object is an entity that has attributes, behavior, and identity. Objects are members of a class.
Objects are accessed, created or deleted during program run-time.


Declaration of an Object in OOPs
ClassName objectName=new ClassName();
Car objCar= new Car();
Attribute in OOPs: Attributes define the characteristics of a class. In Class Program attribute can be a string or it can be a integer. 
Behavior in OOPS:  Every object has behavior.
Identity in OOPS:  Each time an object is created the object identity is been defined.

Advantages of object oriented programming:

• Code Re-usability(Polymorphism,Interfaces): In OOPs objects created in one program can be reused in different programs.
• Code extensibility: for addding new features or modifying existing objects can be solved by introducing new objects.
• Catch errors at compile time rather than at runtime.
• Maintainability :objects can be maintained separately, so u can easily fix errors.
• Imrove error handling:We can use exceptions to improve error handling.
• Modularity: can create seperate Modules.
• Modifiability:it is easy to make minor changes in some classes as Changes inside a class do not affect any other part of a program.

Unified Modeling Language(UML)

Object Oriented Programming

Introduction to Object-Oriented Programming Using PHP.This page  will describes the term `object-oriented programming`.let's start with few basic concepts before you can begin writing any code.
Object-oriented programming is a method of programming based on a hierarchy of classes, and well-defined objects.


Brief overview of object-oriented concepts and terminology:

• Object.
• Class.
• Inheritance.
• Interface.
• Package.

What’s the special meaning of __sleep and __wakeup?


__sleep returns the array of all the variables than need to be saved.
 __wakeup retrieves them.


__sleep() and __wakeup() run prior to serialize() and unserialize() respectively.


Example:
<?php
class DBConn
{
    protected $conn;
    private $host, $username, $password, $db;
    
    public function __construct($host, $username, $password, $db)
    {
        $this->host = $host;
        $this->username = $username;
        $this->password = $password;
        $this->db = $db;
        $this->connect();
    }
    
    private function connect()
    {
        $this->conn = mysql_connect($this->host, $this->username, $this->password);
        mysql_select_db($this->db, $this->conn);
    }
    
    public function __sleep()
    {
        return array('host', 'username', 'password', 'db');
    }
    
    public function __wakeup()
    {
        $this->connect();
    }
}
?>

parent::constructor($value)


Example:



class parentClass
{
     function __construct()
   {
    }
}


class chClass extends parentClass
{
   function __construct()
   {
      parent::__construct(); //call a constructor for a parent class
       }
}

Ternary conditional operator:
Expression preceding the ? is evaluated, if it’s true, then the expression preceding  the : is executed, otherwise, the expression following : is executed.


Syntax:
Condition ? value if true :value if false;


Example:
<?php
$id = isset($_POST['name']) ?  $_POST['name'] : false;
?>

Yes you can compare string and integer in PHP  as  internally PHP will cast everything to the integer type, so numbers 100 and 100 will be compared.

In this section, I will explain how to define a constant in PHP.


define("Test","Hello Rajesh Sharma! How are you today?");

The constant() function returns the value of a constant.
Syntax:
<?php
//define a constant
define("Test","Hello Rajesh Sharma! How are you today?");


echo constant("Test");
?>

You can pass a variable by reference to a function.
Note: you can't pass NULL to a function by reference, unless it's as a default value.




<?php 
function test(&$arg = 1) { 
    if ($arg == 1) { 
       echo  $arg; 
    } 
} 
test(); 
?> 

I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem?

What’s the difference between include and require in PHP?

require(): If the file is not found by require(), it will cause a fatal error and halt the execution of the script.
include(): If the file is not found by include(), a warning will be issued, but execution will continue.