What is the use of history object?
By using the history object you can change or switch back to history pages or forward from current page to another page.
What is an Event Bubbling in Javascript?
When an event is fired on an HTML element, the execution starts from that event and goes to its parent element. From there, the execution passes to its parent element and so on till the body element.
What does window.print() do in Javascript?
The print() function from window object prints the current web page when executed.
How can a Javascript code redirect the user to a different page?
The window.location is assigned a value; i.e., a web link. On its execution, the Javascript code can redirect the user to the mentioned web link.
What are Cookies in Javascript?
A Cookie is a variable that is stored on a client's/visitors machine. Using Cookies, the servers can identify the client and the client's transactions.
How do Javascript primitive/object types passed in functions?
Primitive types in Javascript are passed by value; whereas, object types are passed by reference.
What is NaN in Javascript?
NaN is a short form of Not a Number. When a string or something else is being converted into a number and that cannot be done, then we get to see NaN. A strange thing about NaN is that it is not equal to anything including itself.
List out all the falsifying tokens in Javascript.
There are 6 tokens that falsify in Javascript and they are false, null, undefined, 0, NaN.
What is Currying in Javascript?
A partial invocation of a Javascript function is called Currying. Few arguments of a function are processed and a function is returned. Few more arguments are added by the returning function.
When do we use JSON.stringify()?
The JSON.stringify() method is used to convert a Javascript data to a string.
What does unshift() function do in Javascript?
Just like push() which inserts elements into an array at the end of it, the unshift() function inserts elements at the beginning of an array.
Why jQuery is needed?
jQuery is needed for the following list:
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
Whether jQuery HTML work for both HTML and XML documents?
No, jQuery HTML only works for HTML documents not for XML Documents.
What are the methods used to provide effects?
Some of the effects methods are:
Show()
Hide()
Toggle()
FadeIn() and
FadeOut()
How can you test the Ajax code?
JSUnit is the client side javascript code used as part of JUnit. JSUnit has been used for Ajax code.
Is Ajax said to be a technology platform or is it an architectural style?
Ajax supports both technology and as architectural style.
How can AJAX applications be debugged?
Two tools are used for debugging:
Fiddler for IE
Firebug for Mozilla.
What is Script Manager?
Script Manager helps manage the client side script of AJAX. Script Manager acts as a mediator as AJAX depends on JavaScript. Every page that uses AJAX has a Script Manager to enable AJAX libraries.
How Ajax objects can be created?
Following syntax can be used to create Ajax objects:
Var sample = New ajaxObject(‘path of the page’)
What are all the different data types that JSON supports?
JSON supports following data types:
String
Number
Boolean
Array
Object
Null
What are the goals of Ajax?
The basic goals of ASP.NET Ajax are:
Reduced web server hits
Reduced Network load
Interactive user interface
Platform and architecture neutrality
Support for both synchronous and asynchronous communication
Provide a server- and client-side framework
What is the difference between proxied and proxyless calls in AJAX?
Proxied calls are made through stub objects which can be called from PHP classes on the JavaScript side in AJAX.
Proxyless calls are made using utility JavaScript functions like HTML_AJAX.replace() and HTML_AJAX.append() in AJAX.
Consider the two functions below. Will they both return the same thing? Why or why not?
function foo1()
{
return {
bar: "hello"
};
}
function foo2()
{
return
{
bar: "hello"
};
}
Surprisingly, these two functions will not return the same thing. Rather:
console.log("foo1 returns:");
console.log(foo1());
console.log("foo2 returns:");
console.log(foo2());
will yield:
foo1 returns:
Object {bar: "hello"}
foo2 returns:
undefined
Not only is this surprising, but what makes this particularly gnarly is that foo2() returns undefined without any error being thrown.
The reason for this has to do with the fact that semicolons are technically optional in JavaScript (although omitting them is generally really bad form). As a result, when the line containing the return statement (with nothing else on the line) is encountered in foo2(), a semicolon is automatically inserted immediately after the return statement.
No error is thrown since the remainder of the code is perfectly valid, even though it doesn’t ever get invoked or do anything (it is simply an unused code block that defines a property bar which is equal to the string "hello").
This behavior also argues for following the convention of placing an opening curly brace at the end of a line in JavaScript, rather than on the beginning of a new line. As shown here, this becomes more than just a stylistic preference in JavaScript.
What is NaN? What is its type? How can you reliably test if a value is equal to NaN?
The NaN property represents a value that is “not a number”. This special value results from an operation that could not be performed either because one of the operands was non-numeric (e.g., "abc" / 4), or because the result of the operation is non-numeric.
While this seems straightforward enough, there are a couple of somewhat surprising characteristics of NaN that can result in hair-pulling bugs if one is not aware of them.
For one thing, although NaN means “not a number”, its type is, believe it or not, Number:
console.log(typeof NaN === "number"); // logs "true"
Additionally, NaN compared to anything – even itself! – is false:
console.log(NaN === NaN); // logs "false"
A semi-reliable way to test whether a number is equal to NaN is with the built-in function isNaN(), but even using isNaN() is an imperfect solution.
A better solution would either be to use value !== value, which would only produce true if the value is equal to NaN. Also, ES6 offers a new Number.isNaN() function, which is a different and more reliable than the old global isNaN() function.
What will the code below output? Explain your answer.
console.log(0.1 + 0.2);
console.log(0.1 + 0.2 == 0.3);
An educated answer to this question would simply be: “You can’t be sure. it might print out 0.3 and true, or it might not. Numbers in JavaScript are all treated with floating point precision, and as such, may not always yield the expected results.”
The example provided above is classic case that demonstrates this issue. Surprisingly, it will print out:
0.30000000000000004
false
A typical solution is to compare the absolute difference between two numbers with the special constant Number.EPSILON:
function areTheNumbersAlmostEqual(num1, num2) {
return Math.abs( num1 - num2 ) < Number.EPSILON;
}
console.log(areTheNumbersAlmostEqual(0.1 + 0.2, 0.3));
Discuss possible ways to write a function isInteger(x) that determines if x is an integer.
This may sound trivial and, in fact, it is trivial with ECMAscript 6 which introduces a new Number.isInteger() function for precisely this purpose. However, prior to ECMAScript 6, this is a bit more complicated, since no equivalent of the Number.isInteger() method is provided.
The issue is that, in the ECMAScript specification, integers only exist conceptually; i.e., numeric values are always stored as floating point values.
With that in mind, the simplest and cleanest pre-ECMAScript-6 solution (which is also sufficiently robust to return false even if a non-numeric value such as a string or null is passed to the function) would be the following use of the bitwise XOR operator:
function isInteger(x) { return (x ^ 0) === x; }
The following solution would also work, although not as elegant as the one above:
function isInteger(x) { return Math.round(x) === x; }
Note that Math.ceil() or Math.floor() could be used equally well (instead of Math.round()) in the above implementation.
Or alternatively:
function isInteger(x) { return (typeof x === 'number') && (x % 1 === 0); }
One fairly common incorrect solution is the following:
function isInteger(x) { return parseInt(x, 10) === x; }
While this parseInt-based approach will work well for many values of x, once x becomes quite large, it will fail to work properly. The problem is that parseInt() coerces its first parameter to a string before parsing digits. Therefore, once the number becomes sufficiently large, its string representation will be presented in exponential form (e.g., 1e+21). Accordingly, parseInt() will then try to parse 1e+21, but will stop parsing when it reaches the e character and will therefore return a value of 1. Observe:
> String(1000000000000000000000)
'1e+21'
> parseInt(1000000000000000000000, 10)
1
> parseInt(1000000000000000000000, 10) === 1000000000000000000000
false.
By using the history object you can change or switch back to history pages or forward from current page to another page.
What is an Event Bubbling in Javascript?
When an event is fired on an HTML element, the execution starts from that event and goes to its parent element. From there, the execution passes to its parent element and so on till the body element.
What does window.print() do in Javascript?
The print() function from window object prints the current web page when executed.
How can a Javascript code redirect the user to a different page?
The window.location is assigned a value; i.e., a web link. On its execution, the Javascript code can redirect the user to the mentioned web link.
What are Cookies in Javascript?
A Cookie is a variable that is stored on a client's/visitors machine. Using Cookies, the servers can identify the client and the client's transactions.
 |
| Naver JavaScript Most Frequently Asked Latest Interview Questions Answers |
How do Javascript primitive/object types passed in functions?
Primitive types in Javascript are passed by value; whereas, object types are passed by reference.
What is NaN in Javascript?
NaN is a short form of Not a Number. When a string or something else is being converted into a number and that cannot be done, then we get to see NaN. A strange thing about NaN is that it is not equal to anything including itself.
List out all the falsifying tokens in Javascript.
There are 6 tokens that falsify in Javascript and they are false, null, undefined, 0, NaN.
What is Currying in Javascript?
A partial invocation of a Javascript function is called Currying. Few arguments of a function are processed and a function is returned. Few more arguments are added by the returning function.
When do we use JSON.stringify()?
The JSON.stringify() method is used to convert a Javascript data to a string.
What does unshift() function do in Javascript?
Just like push() which inserts elements into an array at the end of it, the unshift() function inserts elements at the beginning of an array.
Why jQuery is needed?
jQuery is needed for the following list:
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
Whether jQuery HTML work for both HTML and XML documents?
No, jQuery HTML only works for HTML documents not for XML Documents.
What are the methods used to provide effects?
Some of the effects methods are:
Show()
Hide()
Toggle()
FadeIn() and
FadeOut()
JSUnit is the client side javascript code used as part of JUnit. JSUnit has been used for Ajax code.
Is Ajax said to be a technology platform or is it an architectural style?
Ajax supports both technology and as architectural style.
How can AJAX applications be debugged?
Two tools are used for debugging:
Fiddler for IE
Firebug for Mozilla.
What is Script Manager?
Script Manager helps manage the client side script of AJAX. Script Manager acts as a mediator as AJAX depends on JavaScript. Every page that uses AJAX has a Script Manager to enable AJAX libraries.
How Ajax objects can be created?
Following syntax can be used to create Ajax objects:
Var sample = New ajaxObject(‘path of the page’)
What are all the different data types that JSON supports?
JSON supports following data types:
String
Number
Boolean
Array
Object
Null
What are the goals of Ajax?
The basic goals of ASP.NET Ajax are:
Reduced web server hits
Reduced Network load
Interactive user interface
Platform and architecture neutrality
Support for both synchronous and asynchronous communication
Provide a server- and client-side framework
What is the difference between proxied and proxyless calls in AJAX?
Proxied calls are made through stub objects which can be called from PHP classes on the JavaScript side in AJAX.
Proxyless calls are made using utility JavaScript functions like HTML_AJAX.replace() and HTML_AJAX.append() in AJAX.
Consider the two functions below. Will they both return the same thing? Why or why not?
function foo1()
{
return {
bar: "hello"
};
}
function foo2()
{
return
{
bar: "hello"
};
}
Surprisingly, these two functions will not return the same thing. Rather:
console.log("foo1 returns:");
console.log(foo1());
console.log("foo2 returns:");
console.log(foo2());
will yield:
foo1 returns:
Object {bar: "hello"}
foo2 returns:
undefined
Not only is this surprising, but what makes this particularly gnarly is that foo2() returns undefined without any error being thrown.
The reason for this has to do with the fact that semicolons are technically optional in JavaScript (although omitting them is generally really bad form). As a result, when the line containing the return statement (with nothing else on the line) is encountered in foo2(), a semicolon is automatically inserted immediately after the return statement.
No error is thrown since the remainder of the code is perfectly valid, even though it doesn’t ever get invoked or do anything (it is simply an unused code block that defines a property bar which is equal to the string "hello").
This behavior also argues for following the convention of placing an opening curly brace at the end of a line in JavaScript, rather than on the beginning of a new line. As shown here, this becomes more than just a stylistic preference in JavaScript.
What is NaN? What is its type? How can you reliably test if a value is equal to NaN?
The NaN property represents a value that is “not a number”. This special value results from an operation that could not be performed either because one of the operands was non-numeric (e.g., "abc" / 4), or because the result of the operation is non-numeric.
While this seems straightforward enough, there are a couple of somewhat surprising characteristics of NaN that can result in hair-pulling bugs if one is not aware of them.
For one thing, although NaN means “not a number”, its type is, believe it or not, Number:
console.log(typeof NaN === "number"); // logs "true"
Additionally, NaN compared to anything – even itself! – is false:
console.log(NaN === NaN); // logs "false"
A semi-reliable way to test whether a number is equal to NaN is with the built-in function isNaN(), but even using isNaN() is an imperfect solution.
A better solution would either be to use value !== value, which would only produce true if the value is equal to NaN. Also, ES6 offers a new Number.isNaN() function, which is a different and more reliable than the old global isNaN() function.
What will the code below output? Explain your answer.
console.log(0.1 + 0.2);
console.log(0.1 + 0.2 == 0.3);
An educated answer to this question would simply be: “You can’t be sure. it might print out 0.3 and true, or it might not. Numbers in JavaScript are all treated with floating point precision, and as such, may not always yield the expected results.”
The example provided above is classic case that demonstrates this issue. Surprisingly, it will print out:
0.30000000000000004
false
A typical solution is to compare the absolute difference between two numbers with the special constant Number.EPSILON:
function areTheNumbersAlmostEqual(num1, num2) {
return Math.abs( num1 - num2 ) < Number.EPSILON;
}
console.log(areTheNumbersAlmostEqual(0.1 + 0.2, 0.3));
Discuss possible ways to write a function isInteger(x) that determines if x is an integer.
This may sound trivial and, in fact, it is trivial with ECMAscript 6 which introduces a new Number.isInteger() function for precisely this purpose. However, prior to ECMAScript 6, this is a bit more complicated, since no equivalent of the Number.isInteger() method is provided.
The issue is that, in the ECMAScript specification, integers only exist conceptually; i.e., numeric values are always stored as floating point values.
With that in mind, the simplest and cleanest pre-ECMAScript-6 solution (which is also sufficiently robust to return false even if a non-numeric value such as a string or null is passed to the function) would be the following use of the bitwise XOR operator:
function isInteger(x) { return (x ^ 0) === x; }
The following solution would also work, although not as elegant as the one above:
function isInteger(x) { return Math.round(x) === x; }
Note that Math.ceil() or Math.floor() could be used equally well (instead of Math.round()) in the above implementation.
Or alternatively:
function isInteger(x) { return (typeof x === 'number') && (x % 1 === 0); }
One fairly common incorrect solution is the following:
function isInteger(x) { return parseInt(x, 10) === x; }
While this parseInt-based approach will work well for many values of x, once x becomes quite large, it will fail to work properly. The problem is that parseInt() coerces its first parameter to a string before parsing digits. Therefore, once the number becomes sufficiently large, its string representation will be presented in exponential form (e.g., 1e+21). Accordingly, parseInt() will then try to parse 1e+21, but will stop parsing when it reaches the e character and will therefore return a value of 1. Observe:
> String(1000000000000000000000)
'1e+21'
> parseInt(1000000000000000000000, 10)
1
> parseInt(1000000000000000000000, 10) === 1000000000000000000000
false.
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