Splunk Technology JavaScript Most Frequently Asked Latest Interview Questions Answers
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 difference between ViewState and SessionState?
‘ViewState’ is specific to a page in a session.
‘SessionState’ is specific to user specific data that can be accessed across all pages in the web application.
What is === operator?
=== is called as strict equality operator which returns true when the two operands are having the same value without any type conversion.
Explain how can you submit a form using JavaScript?
To submit a form using JavaScript use document.form[0].submit();
document.form[0].submit();
Does JavaScript support automatic type conversion?
Yes JavaScript does support automatic type conversion, it is the common way of type conversion used by JavaScript developers
How can the style/class of an element be changed?
It can be done in the following way:
document.getElementById(“myText”).style.fontSize = “20?;
or
document.getElementById(“myText”).className = “anyclass”;
Explain how to read and write a file using JavaScript?
There are two ways to read and write a file using JavaScript
Using JavaScript extensions
Using a web page and Active X objects
What are all the looping structures in JavaScript?
Following are looping structures in Javascript:
For
While
do-while loops
What is called Variable typing in Javascript?
Variable typing is used to assign a number to a variable and the same variable can be assigned to a string.
Example
i = 10;
i = "string";
This is called variable typing.
How can you convert the string of any base to integer in JavaScript?
The parseInt() function is used to convert numbers between different bases. parseInt() takes the string to be converted as its first parameter, and the second parameter is the base of the given string.
In order to convert 4F (of base 16) to integer, the code used will be –
parseInt ("4F", 16);
Explain the difference between “==” and “===”?
“==” checks only for equality in value whereas “===” is a stricter equality test and returns false if either the value or the type of the two variables are different.
What would be the result of 3+2+”7″?
Since 3 and 2 are integers, they will be added numerically. And since 7 is a string, its concatenation will be done. So the result would be 57.
In what order will the numbers 1-4 be logged to the console when the code below is executed? Why?
(function() {
console.log(1);
setTimeout(function(){console.log(2)}, 1000);
setTimeout(function(){console.log(3)}, 0);
console.log(4);
})();
The values will be logged in the following order:
1
4
3
2
Let’s first explain the parts of this that are presumably more obvious:
1 and 4 are displayed first since they are logged by simple calls to console.log() without any delay
2 is displayed after 3 because 2 is being logged after a delay of 1000 msecs (i.e., 1 second) whereas 3 is being logged after a delay of 0 msecs.
OK, fine. But if 3 is being logged after a delay of 0 msecs, doesn’t that mean that it is being logged right away? And, if so, shouldn’t it be logged before 4, since 4 is being logged by a later line of code?
The answer has to do with properly understanding JavaScript events and timing.
The browser has an event loop which checks the event queue and processes pending events. For example, if an event happens in the background (e.g., a script onload event) while the browser is busy (e.g., processing an onclick), the event gets appended to the queue. When the onclick handler is complete, the queue is checked and the event is then handled (e.g., the onload script is executed).
Similarly, setTimeout() also puts execution of its referenced function into the event queue if the browser is busy.
When a value of zero is passed as the second argument to setTimeout(), it attempts to execute the specified function “as soon as possible”. Specifically, execution of the function is placed on the event queue to occur on the next timer tick. Note, though, that this is not immediate; the function is not executed until the next tick. That’s why in the above example, the call to console.log(4) occurs before the call to console.log(3) (since the call to console.log(3) is invoked via setTimeout, so it is slightly delayed).
Write a simple function (less than 160 characters) that returns a boolean indicating whether or not a string is a palindrome.
The following one line function will return true if str is a palindrome; otherwise, it returns false.
function isPalindrome(str) {
str = str.replace(/\W/g, '').toLowerCase();
return (str == str.split('').reverse().join(''));
}
For example:
console.log(isPalindrome("level")); // logs 'true'
console.log(isPalindrome("levels")); // logs 'false'
console.log(isPalindrome("A car, a man, a maraca")); // logs 'true'
Write a sum method which will work properly when invoked using either syntax below.
console.log(sum(2,3)); // Outputs 5
console.log(sum(2)(3)); // Outputs 5
There are (at least) two ways to do this:
METHOD 1
function sum(x) {
if (arguments.length == 2) {
return arguments[0] + arguments[1];
} else {
return function(y) { return x + y; };
}
}
In JavaScript, functions provide access to an arguments object which provides access to the actual arguments passed to a function. This enables us to use the length property to determine at runtime the number of arguments passed to the function.
If two arguments are passed, we simply add them together and return.
Otherwise, we assume it was called in the form sum(2)(3), so we return an anonymous function that adds together the argument passed to sum() (in this case 2) and the argument passed to the anonymous function (in this case 3).
METHOD 2
function sum(x, y) {
if (y !== undefined) {
return x + y;
} else {
return function(y) { return x + y; };
}
}
When a function is invoked, JavaScript does not require the number of arguments to match the number of arguments in the function definition. If the number of arguments passed exceeds the number of arguments in the function definition, the excess arguments will simply be ignored. On the other hand, if the number of arguments passed is less than the number of arguments in the function definition, the missing arguments will have a value of undefined when referenced within the function. So, in the above example, by simply checking if the 2nd argument is undefined, we can determine which way the function was invoked and proceed accordingly.
How can we handle concurrent requests?
Javascript functions should be written to handle concurrent requests and call back function can be passed as a parameter. Those parameters are passed to AjaxInteraction(URL, callback) 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.
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
How many types of ready states in Ajax?
There are four ready states in Ajax:
Initialization
Request
Process
Ready.
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.
 |
| Splunk Technology JavaScript Most Frequently Asked Latest Interview Questions Answers |
Which symbol is used for comments in Javascript?
// for Single line comments and
/* Multi
Line
Comment
*/
What is the difference between ViewState and SessionState?
‘ViewState’ is specific to a page in a session.
‘SessionState’ is specific to user specific data that can be accessed across all pages in the web application.
What is === operator?
=== is called as strict equality operator which returns true when the two operands are having the same value without any type conversion.
Explain how can you submit a form using JavaScript?
To submit a form using JavaScript use document.form[0].submit();
document.form[0].submit();
Does JavaScript support automatic type conversion?
Yes JavaScript does support automatic type conversion, it is the common way of type conversion used by JavaScript developers
How can the style/class of an element be changed?
It can be done in the following way:
document.getElementById(“myText”).style.fontSize = “20?;
or
document.getElementById(“myText”).className = “anyclass”;
Explain how to read and write a file using JavaScript?
There are two ways to read and write a file using JavaScript
Using JavaScript extensions
Using a web page and Active X objects
What are all the looping structures in JavaScript?
Following are looping structures in Javascript:
For
While
do-while loops
What is called Variable typing in Javascript?
Variable typing is used to assign a number to a variable and the same variable can be assigned to a string.
Example
i = 10;
i = "string";
This is called variable typing.
How can you convert the string of any base to integer in JavaScript?
The parseInt() function is used to convert numbers between different bases. parseInt() takes the string to be converted as its first parameter, and the second parameter is the base of the given string.
In order to convert 4F (of base 16) to integer, the code used will be –
parseInt ("4F", 16);
Explain the difference between “==” and “===”?
“==” checks only for equality in value whereas “===” is a stricter equality test and returns false if either the value or the type of the two variables are different.
What would be the result of 3+2+”7″?
Since 3 and 2 are integers, they will be added numerically. And since 7 is a string, its concatenation will be done. So the result would be 57.
In what order will the numbers 1-4 be logged to the console when the code below is executed? Why?
(function() {
console.log(1);
setTimeout(function(){console.log(2)}, 1000);
setTimeout(function(){console.log(3)}, 0);
console.log(4);
})();
The values will be logged in the following order:
1
4
3
2
Let’s first explain the parts of this that are presumably more obvious:
1 and 4 are displayed first since they are logged by simple calls to console.log() without any delay
2 is displayed after 3 because 2 is being logged after a delay of 1000 msecs (i.e., 1 second) whereas 3 is being logged after a delay of 0 msecs.
OK, fine. But if 3 is being logged after a delay of 0 msecs, doesn’t that mean that it is being logged right away? And, if so, shouldn’t it be logged before 4, since 4 is being logged by a later line of code?
The answer has to do with properly understanding JavaScript events and timing.
The browser has an event loop which checks the event queue and processes pending events. For example, if an event happens in the background (e.g., a script onload event) while the browser is busy (e.g., processing an onclick), the event gets appended to the queue. When the onclick handler is complete, the queue is checked and the event is then handled (e.g., the onload script is executed).
Similarly, setTimeout() also puts execution of its referenced function into the event queue if the browser is busy.
When a value of zero is passed as the second argument to setTimeout(), it attempts to execute the specified function “as soon as possible”. Specifically, execution of the function is placed on the event queue to occur on the next timer tick. Note, though, that this is not immediate; the function is not executed until the next tick. That’s why in the above example, the call to console.log(4) occurs before the call to console.log(3) (since the call to console.log(3) is invoked via setTimeout, so it is slightly delayed).
Write a simple function (less than 160 characters) that returns a boolean indicating whether or not a string is a palindrome.
The following one line function will return true if str is a palindrome; otherwise, it returns false.
function isPalindrome(str) {
str = str.replace(/\W/g, '').toLowerCase();
return (str == str.split('').reverse().join(''));
}
For example:
console.log(isPalindrome("level")); // logs 'true'
console.log(isPalindrome("levels")); // logs 'false'
console.log(isPalindrome("A car, a man, a maraca")); // logs 'true'
Write a sum method which will work properly when invoked using either syntax below.
console.log(sum(2,3)); // Outputs 5
console.log(sum(2)(3)); // Outputs 5
There are (at least) two ways to do this:
METHOD 1
function sum(x) {
if (arguments.length == 2) {
return arguments[0] + arguments[1];
} else {
return function(y) { return x + y; };
}
}
In JavaScript, functions provide access to an arguments object which provides access to the actual arguments passed to a function. This enables us to use the length property to determine at runtime the number of arguments passed to the function.
If two arguments are passed, we simply add them together and return.
Otherwise, we assume it was called in the form sum(2)(3), so we return an anonymous function that adds together the argument passed to sum() (in this case 2) and the argument passed to the anonymous function (in this case 3).
METHOD 2
function sum(x, y) {
if (y !== undefined) {
return x + y;
} else {
return function(y) { return x + y; };
}
}
When a function is invoked, JavaScript does not require the number of arguments to match the number of arguments in the function definition. If the number of arguments passed exceeds the number of arguments in the function definition, the excess arguments will simply be ignored. On the other hand, if the number of arguments passed is less than the number of arguments in the function definition, the missing arguments will have a value of undefined when referenced within the function. So, in the above example, by simply checking if the 2nd argument is undefined, we can determine which way the function was invoked and proceed accordingly.
How can we handle concurrent requests?
Javascript functions should be written to handle concurrent requests and call back function can be passed as a parameter. Those parameters are passed to AjaxInteraction(URL, callback) 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.
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
How many types of ready states in Ajax?
There are four ready states in Ajax:
Initialization
Request
Process
Ready.
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