Birlasoft JavaScript Most Frequently Asked Latest Interview Questions Answers
Define the role of the Update Panel?
Update Panel is used to add functionality to the existing ASP.NET applications. By using partial page rendering, it can be used to update the content. Refresh can be made for the partial page instead of whole page.
Can we use nested update panel in Ajax?
Yes, we can use nested update panel in Ajax. Update panels can be nested to have more control over the Page Refresh.
What are the types of post back in Ajax?
There are two types of post backs:
Synchronous Postback
Asynchronous Postback
How can we handle exception handling in Ajax?
ErrorTemplate which is the child tag of Script Manager is used to handle exception handling in Ajax.
What are the components of the ASP.NET Ajax Client Library?
Following components are used in Ajax client library:
Component Layer
Core Services Layer
Browser Compatibility Layer
What are the controls of the Script Management group?
The controls of script Management group are:
ScriptManager
ScriptManagerProxy
What is the issue with this code and how can it be fixed.
The code will output:
undefined
John Doe
The first console.log prints undefined because we are extracting the method from the hero object, so stoleSecretIdentity() is being invoked in the global context (i.e., the window object) where the _name property does not exist.
One way to fix the stoleSecretIdentity() function is as follows:
var stoleSecretIdentity = hero.getSecretIdentity.bind(hero);
Create a function that, given a DOM Element on the page, will visit the element itself and all of its descendents (not just its immediate children). For each element visited, the function should pass that element to a provided callback function.
The arguments to the function should be:
a DOM element
a callback function (that takes a DOM element as its argument)
Visiting all elements in a tree (DOM) is a classic Depth-First-Search algorithm application. Here’s an example solution:
function Traverse(p_element,p_callback) {
p_callback(p_element);
var list = p_element.children;
for (var i = 0; i < list.length; i++) {
Traverse(list[i],p_callback); // recursive call
}
}
Testing your this knowledge in JavaScript: What is the output of the following code?
var length = 10;
function fn() {
console.log(this.length);
}
var obj = {
length: 5,
method: function(fn) {
fn();
arguments[0]();
}
};
obj.method(fn, 1);
Output:
10
2
Why isn’t it 10 and 5?
In the first place, as fn is passed as a parameter to the function method, the scope (this) of the function fn is window. var length = 10; is declared at the window level. It also can be accessed as window.length or length or this.length (when this === window.)
method is bound to Object obj, and obj.method is called with parameters fn and 1. Though method is accepting only one parameter, while invoking it has passed two parameters; the first is a function callback and other is just a number.
When fn() is called inside method, which was passed the function as a parameter at the global level, this.length will have access to var length = 10 (declared globally) not length = 5 as defined in Object obj.
Now, we know that we can access any number of arguments in a JavaScript function using the arguments[] array.
Hence arguments[0]() is nothing but calling fn(). Inside fn now, the scope of this function becomes the arguments array, and logging the length of arguments[] will return 2.
Hence the output will be as above.
Consider the following code. What will the output be, and why?
(function () {
try {
throw new Error();
} catch (x) {
var x = 1, y = 2;
console.log(x);
}
console.log(x);
console.log(y);
})();
1
undefined
2
var statements are hoisted (without their value initialization) to the top of the global or function scope it belongs to, even when it’s inside a with or catch block. However, the error’s identifier is only visible inside the catch block. It is equivalent to:
(function () {
var x, y; // outer and hoisted
try {
throw new Error();
} catch (x /* inner */) {
x = 1; // inner x, not the outer one
y = 2; // there is only one y, which is in the outer scope
console.log(x /* inner */);
}
console.log(x);
console.log(y);
})();
What will be the output of this code?
var x = 21;
var girl = function () {
console.log(x);
var x = 20;
};
girl ();
Neither 21, nor 20, the result is undefined
It’s because JavaScript initialization is not hoisted.
(Why doesn’t it show the global value of 21? The reason is that when the function is executed, it checks that there’s a local x variable present but doesn’t yet declare it, so it won’t look for global one.)
What is the difference between size and length of jQuery?
Size and length both returns the number of element in an object. But length is faster than the size because length is a property and size is a method.
Can we add more than one ‘document.ready’ function in a page?
Yes, we can add more than one document.ready function in a page. But, body.onload can be added once in a page.
What is the use of jQuery load method?
jQuery load method is a powerful AJAX method which is used to load the data from a server and assign the data into the element without loading the page.
Whether our own specific characters are used in place of $ in jQuery?
Yes, We can use our own variable in place of $ by using the method called no Conflict () method.
var sample = $.noConflict()
What are the four parameters used for jQuery Ajax method?
The four parameters are
URL – Need to specify the URL to send the request
type – Specifies type of request(Get or Post)
data – Specifies data to be sent to server
Cache – Whether the browser should cache the requested page
What is the use of jQuery filter?
The jQuery filter is used to filter the certain values from the object list based on the criteria. Example is to filter certain products from the master list of products in a cart website.
Which program is useful for testing jQuery?
QUnit is used to test jQuery and it is very easy and efficient.
What is CDN?
CDN is abbreviated as Content Distribution network and it is said to be a group of companies in different location with network containing copies of data files to maximize bandwidth in accessing the data.
What are the two types of CDNs?
There are two types of CDNs:
Microsoft – Load jQuery from Ajax CDN
Google – Load jQuery from Google libraries API
Which sign is used as a shortcut for jQuery?
Dollar ($) sign is used as a shortcut for jQuery.
Is jQuery is a client or server scripting?
jQuery is a client scripting.
What is the script build up by jQuery?
jQuery is a Javascript file and it is single javascript file that contains common DOM, event effects and Ajax functions.
How can we debug jQuery?
There are two ways to debug jQuery:
Debugger keyword
Add the debugger to the line from where we have to start debugging and then run Visual Studio in Debug mode with F5 function key.
Insert a break point after attaching the process
What are all the ways to include jQuery in a page?
Following are the ways to include jQuery in a page:
Local copy inside script tag
Remote copy of jQuery.com
Remote copy of Ajax API
Local copy of script manager control
Embedded script using client script object.
Define the role of the Update Panel?
Update Panel is used to add functionality to the existing ASP.NET applications. By using partial page rendering, it can be used to update the content. Refresh can be made for the partial page instead of whole page.
Can we use nested update panel in Ajax?
Yes, we can use nested update panel in Ajax. Update panels can be nested to have more control over the Page Refresh.
What are the types of post back in Ajax?
There are two types of post backs:
Synchronous Postback
Asynchronous Postback
How can we handle exception handling in Ajax?
ErrorTemplate which is the child tag of Script Manager is used to handle exception handling in Ajax.
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| Birlasoft JavaScript Most Frequently Asked Latest Interview Questions Answers |
What are the components of the ASP.NET Ajax Client Library?
Following components are used in Ajax client library:
Component Layer
Core Services Layer
Browser Compatibility Layer
What are the controls of the Script Management group?
The controls of script Management group are:
ScriptManager
ScriptManagerProxy
What is the issue with this code and how can it be fixed.
The code will output:
undefined
John Doe
The first console.log prints undefined because we are extracting the method from the hero object, so stoleSecretIdentity() is being invoked in the global context (i.e., the window object) where the _name property does not exist.
One way to fix the stoleSecretIdentity() function is as follows:
var stoleSecretIdentity = hero.getSecretIdentity.bind(hero);
Create a function that, given a DOM Element on the page, will visit the element itself and all of its descendents (not just its immediate children). For each element visited, the function should pass that element to a provided callback function.
The arguments to the function should be:
a DOM element
a callback function (that takes a DOM element as its argument)
Visiting all elements in a tree (DOM) is a classic Depth-First-Search algorithm application. Here’s an example solution:
function Traverse(p_element,p_callback) {
p_callback(p_element);
var list = p_element.children;
for (var i = 0; i < list.length; i++) {
Traverse(list[i],p_callback); // recursive call
}
}
Testing your this knowledge in JavaScript: What is the output of the following code?
var length = 10;
function fn() {
console.log(this.length);
}
var obj = {
length: 5,
method: function(fn) {
fn();
arguments[0]();
}
};
obj.method(fn, 1);
Output:
10
2
Why isn’t it 10 and 5?
In the first place, as fn is passed as a parameter to the function method, the scope (this) of the function fn is window. var length = 10; is declared at the window level. It also can be accessed as window.length or length or this.length (when this === window.)
method is bound to Object obj, and obj.method is called with parameters fn and 1. Though method is accepting only one parameter, while invoking it has passed two parameters; the first is a function callback and other is just a number.
When fn() is called inside method, which was passed the function as a parameter at the global level, this.length will have access to var length = 10 (declared globally) not length = 5 as defined in Object obj.
Now, we know that we can access any number of arguments in a JavaScript function using the arguments[] array.
Hence arguments[0]() is nothing but calling fn(). Inside fn now, the scope of this function becomes the arguments array, and logging the length of arguments[] will return 2.
Hence the output will be as above.
Consider the following code. What will the output be, and why?
(function () {
try {
throw new Error();
} catch (x) {
var x = 1, y = 2;
console.log(x);
}
console.log(x);
console.log(y);
})();
1
undefined
2
var statements are hoisted (without their value initialization) to the top of the global or function scope it belongs to, even when it’s inside a with or catch block. However, the error’s identifier is only visible inside the catch block. It is equivalent to:
(function () {
var x, y; // outer and hoisted
try {
throw new Error();
} catch (x /* inner */) {
x = 1; // inner x, not the outer one
y = 2; // there is only one y, which is in the outer scope
console.log(x /* inner */);
}
console.log(x);
console.log(y);
})();
What will be the output of this code?
var x = 21;
var girl = function () {
console.log(x);
var x = 20;
};
girl ();
Neither 21, nor 20, the result is undefined
It’s because JavaScript initialization is not hoisted.
(Why doesn’t it show the global value of 21? The reason is that when the function is executed, it checks that there’s a local x variable present but doesn’t yet declare it, so it won’t look for global one.)
What is the difference between size and length of jQuery?
Size and length both returns the number of element in an object. But length is faster than the size because length is a property and size is a method.
Can we add more than one ‘document.ready’ function in a page?
Yes, we can add more than one document.ready function in a page. But, body.onload can be added once in a page.
What is the use of jQuery load method?
jQuery load method is a powerful AJAX method which is used to load the data from a server and assign the data into the element without loading the page.
Whether our own specific characters are used in place of $ in jQuery?
Yes, We can use our own variable in place of $ by using the method called no Conflict () method.
var sample = $.noConflict()
What are the four parameters used for jQuery Ajax method?
The four parameters are
URL – Need to specify the URL to send the request
type – Specifies type of request(Get or Post)
data – Specifies data to be sent to server
Cache – Whether the browser should cache the requested page
What is the use of jQuery filter?
The jQuery filter is used to filter the certain values from the object list based on the criteria. Example is to filter certain products from the master list of products in a cart website.
Which program is useful for testing jQuery?
QUnit is used to test jQuery and it is very easy and efficient.
What is CDN?
CDN is abbreviated as Content Distribution network and it is said to be a group of companies in different location with network containing copies of data files to maximize bandwidth in accessing the data.
What are the two types of CDNs?
There are two types of CDNs:
Microsoft – Load jQuery from Ajax CDN
Google – Load jQuery from Google libraries API
Which sign is used as a shortcut for jQuery?
Dollar ($) sign is used as a shortcut for jQuery.
Is jQuery is a client or server scripting?
jQuery is a client scripting.
What is the script build up by jQuery?
jQuery is a Javascript file and it is single javascript file that contains common DOM, event effects and Ajax functions.
How can we debug jQuery?
There are two ways to debug jQuery:
Debugger keyword
Add the debugger to the line from where we have to start debugging and then run Visual Studio in Debug mode with F5 function key.
Insert a break point after attaching the process
What are all the ways to include jQuery in a page?
Following are the ways to include jQuery in a page:
Local copy inside script tag
Remote copy of jQuery.com
Remote copy of Ajax API
Local copy of script manager control
Embedded script using client script object.