Sonata Software JavaScript Most Frequently Asked Latest Interview Questions Answers
What is the use of jQuery.ajax method ()?
jQuery.ajax method is used for asynchronous HTTP requests.
Where can we download JQuery?
jQuery javascript can be downloaded from jQuery official website – www.jquery.com
Is jQuery is a replacement of JavaScript?
No, jQuery is not a replacement of JavaScript.
What is called chaining?
Chaining is used to connect multiple events and functions in a selector.
Is it possible to break JavaScript Code into several lines?
Breaking within a string statement can be done by the use of a backslash, ‘\’, at the end of the first line
Example:
document.write("This is \a program");
And if you change to a new line when not within a string statement, then javaScript ignores break in line.
Example:
var x=1, y=2,
z=
x+y;
The above code is perfectly fine, though not advisable as it hampers debugging.
Which company developed JavaScript?
Netscape is the software company who developed JavaScript.
What are undeclared and undefined variables?
Undeclared variables are those that do not exist in a program and are not declared. If the program tries to read the value of an undeclared variable, then a runtime error is encountered.
Undefined variables are those that are declared in the program but have not been given any value. If the program tries to read the value of an undefined variable, an undefined value is returned.
Write the code for adding new elements dynamically?
<html>
<head> <title>t1</title>
<script type="text/javascript">
function addNode() { var newP = document.createElement("p");
var textNode = document.createTextNode(" This is a new text node");
newP.appendChild(textNode); document.getElementById("firstP").appendChild(newP); }
</script> </head>
<body> <p id="firstP">firstP<p> </body>
</html>
What are global variables? How are these variable declared and what are the problems associated with using them?
Global variables are those that are available throughout the length of the code, that is, these have no scope. The var keyword is used to declare a local variable or object. If the var keyword is omitted, a global variable is declared.
Example:
// Declare a global globalVariable = “Test”;
The problems that are faced by using global variables are the clash of variable names of local and global scope. Also, it is difficult to debug and test the code that relies on global variables.
What is a prompt box?
A prompt box is a box which allows the user to enter input by providing a text box. Label and box will be provided to enter the text or number.
What is ‘this’ keyword in JavaScript?
‘This’ keyword is used to point at the current object in the code. For instance: If the code is presently at an object created by the help of the ‘new’ keyword, then ‘this’ keyword will point to the object being created.
Explain the working of timers in JavaScript? Also elucidate the drawbacks of using the timer, if any?
Timers are used to execute a piece of code at a set time or also to repeat the code in a given interval of time. This is done by using the functions setTimeout, setInterval and clearInterval.
The setTimeout(function, delay) function is used to start a timer that calls a particular function after the mentioned delay. The setInterval(function, delay) function is used to repeatedly execute the given function in the mentioned delay and only halts when cancelled. The clearInterval(id) function instructs the timer to stop.
Timers are operated within a single thread, and thus events might queue up, waiting to be executed.
Which symbol is used for comments in Javascript?
// for Single line comments and
/* Multi
Line
Comment
*/
What is the name of the DLL that contains Ajax control tool kit?
Ajaxcontroltoolkit.dll is the DLL used for Ajax control tool kit and it can be downloaded from the internet. It can be added in the tool box or copied directly in the bin folder.
What role of #&& in querystring?
# is treated as fragment delimiter to delimit the history state and && precedes is used to check on the information in the query string.
How to control the duration of an Ajax request?
AsyncPostBackTimeout property is used to control the duration of Ajax request. Deafult value of this property is 90 seconds.
Example –
<asp:ScriptManager runat=”server” id=”sample” AsyncPostBackTimeout=”40”/>
1
<asp:ScriptManager runat=”server” id=”sample” AsyncPostBackTimeout=”40”/>
What are the advantages of Ajax?
Following are the advantages of Ajax:
Bandwidth utilization – It saves memory when the data is fetched from the same page.
More interactive
Speeder retrieval of data
What is JSON in Ajax?
JSON is abbreviated as JavaScript Object Notation.
JSON is a safe and reliable data interchange format in JavaScript, which is easy to understand for both users and machines.
What is AJAX Control Extender Toolkit?
AJAX Control Toolkit is one of the extenders that are used to extend or add the functionalities of the ASP.NET controls. The extenders use a block of JavaScript code to add new and enhanced capabilities to the ASP.NET controls.
AJAX Control Extender Toolkit is a free download from site.
Where AJAX cannot be used?
Users cannot use AJAX if
If Page need to show in a search engine
If browser does not support JavaScript
If user wants to create secure application
What are the difference between AJAX and Javascript?
The differences between AJAX and JavaScript are as follows:
AJAX
Javascript
AJAX sends request to the server and does not wait for the response. It performs other operations on the page during that time JavaScript make a request to the server and waits for response
AJAX does not require the page to refresh for downloading the whole page JavaScript manages and controls a Web page after being downloaded
AJAX minimizes the overload on the server since the script needs to request once JavaScript posts a request that updates the script every time.
What is the use of jQuery.ajax method ()?
jQuery.ajax method is used for asynchronous HTTP requests.
Where can we download JQuery?
jQuery javascript can be downloaded from jQuery official website – www.jquery.com
Is jQuery is a replacement of JavaScript?
No, jQuery is not a replacement of JavaScript.
What is called chaining?
Chaining is used to connect multiple events and functions in a selector.
 |
| Sonata Software JavaScript Most Frequently Asked Latest Interview Questions Answers |
Is it possible to break JavaScript Code into several lines?
Breaking within a string statement can be done by the use of a backslash, ‘\’, at the end of the first line
Example:
document.write("This is \a program");
And if you change to a new line when not within a string statement, then javaScript ignores break in line.
Example:
var x=1, y=2,
z=
x+y;
The above code is perfectly fine, though not advisable as it hampers debugging.
Which company developed JavaScript?
Netscape is the software company who developed JavaScript.
What are undeclared and undefined variables?
Undeclared variables are those that do not exist in a program and are not declared. If the program tries to read the value of an undeclared variable, then a runtime error is encountered.
Undefined variables are those that are declared in the program but have not been given any value. If the program tries to read the value of an undefined variable, an undefined value is returned.
Write the code for adding new elements dynamically?
<html>
<head> <title>t1</title>
<script type="text/javascript">
function addNode() { var newP = document.createElement("p");
var textNode = document.createTextNode(" This is a new text node");
newP.appendChild(textNode); document.getElementById("firstP").appendChild(newP); }
</script> </head>
<body> <p id="firstP">firstP<p> </body>
</html>
What are global variables? How are these variable declared and what are the problems associated with using them?
Global variables are those that are available throughout the length of the code, that is, these have no scope. The var keyword is used to declare a local variable or object. If the var keyword is omitted, a global variable is declared.
Example:
// Declare a global globalVariable = “Test”;
The problems that are faced by using global variables are the clash of variable names of local and global scope. Also, it is difficult to debug and test the code that relies on global variables.
What is a prompt box?
A prompt box is a box which allows the user to enter input by providing a text box. Label and box will be provided to enter the text or number.
What is ‘this’ keyword in JavaScript?
‘This’ keyword is used to point at the current object in the code. For instance: If the code is presently at an object created by the help of the ‘new’ keyword, then ‘this’ keyword will point to the object being created.
Explain the working of timers in JavaScript? Also elucidate the drawbacks of using the timer, if any?
Timers are used to execute a piece of code at a set time or also to repeat the code in a given interval of time. This is done by using the functions setTimeout, setInterval and clearInterval.
The setTimeout(function, delay) function is used to start a timer that calls a particular function after the mentioned delay. The setInterval(function, delay) function is used to repeatedly execute the given function in the mentioned delay and only halts when cancelled. The clearInterval(id) function instructs the timer to stop.
Timers are operated within a single thread, and thus events might queue up, waiting to be executed.
Which symbol is used for comments in Javascript?
// for Single line comments and
/* Multi
Line
Comment
*/
What is the name of the DLL that contains Ajax control tool kit?
Ajaxcontroltoolkit.dll is the DLL used for Ajax control tool kit and it can be downloaded from the internet. It can be added in the tool box or copied directly in the bin folder.
What role of #&& in querystring?
# is treated as fragment delimiter to delimit the history state and && precedes is used to check on the information in the query string.
How to control the duration of an Ajax request?
AsyncPostBackTimeout property is used to control the duration of Ajax request. Deafult value of this property is 90 seconds.
Example –
<asp:ScriptManager runat=”server” id=”sample” AsyncPostBackTimeout=”40”/>
1
<asp:ScriptManager runat=”server” id=”sample” AsyncPostBackTimeout=”40”/>
What are the advantages of Ajax?
Following are the advantages of Ajax:
Bandwidth utilization – It saves memory when the data is fetched from the same page.
More interactive
Speeder retrieval of data
What is JSON in Ajax?
JSON is abbreviated as JavaScript Object Notation.
JSON is a safe and reliable data interchange format in JavaScript, which is easy to understand for both users and machines.
What is AJAX Control Extender Toolkit?
AJAX Control Toolkit is one of the extenders that are used to extend or add the functionalities of the ASP.NET controls. The extenders use a block of JavaScript code to add new and enhanced capabilities to the ASP.NET controls.
AJAX Control Extender Toolkit is a free download from site.
Where AJAX cannot be used?
Users cannot use AJAX if
If Page need to show in a search engine
If browser does not support JavaScript
If user wants to create secure application
What are the difference between AJAX and Javascript?
The differences between AJAX and JavaScript are as follows:
AJAX
Javascript
AJAX sends request to the server and does not wait for the response. It performs other operations on the page during that time JavaScript make a request to the server and waits for response
AJAX does not require the page to refresh for downloading the whole page JavaScript manages and controls a Web page after being downloaded
AJAX minimizes the overload on the server since the script needs to request once JavaScript posts a request that updates the script every time.
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