NetApp Most Frequently Asked Latest JavaScript Interview Questions Answers
How many types of triggers are present in update panel?
There are two types of triggers used in update panel:
PostBackTrigger – This works as full postback and it cannot work asynchronously
AsyncPostBackTrigger – Partial post back asynchronously
What are all the controls of Ajax?
Following are the controls of Ajax:
ScriptManager
ScriptManagerProxy
UpdatePanel
UpdateProgress
Timer
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.
What is the use of the ‘this’ keyword?
The keyword ‘this’ refers to the current instance of the object when used inside a function. But, when used outside a function, it refers to the window object.
Is Exception handling possible in Javascript?
With the latest version of Javascript, exception handling is possible; and this can be achieved using the following keywords try, catch and finally.
How is it possible to get the total number of arguments that are passed to a function?
The arguments.length property helps in getting the total number of arguments that are passed to a function.
What is the difference between typeof and instanceof operators in Javascript?
The typeof operator returns a string of what type the operand is. Whereas, the instanceof operator does not work with primitive data types; but works with objects and checks on what type the object is.
What is DOM?
DOM (Document Object Model) is an object-oriented representation of the HTML elements. All the elements (or nodes) are part of window.document.
Expand BOM and explain it.
BOM stands for Browser Object Model. Using BOM interaction with a browser is possible. Default object of the browser is a window.
What is the difference between window and document in Javascript?
Javascript window is a global object which holds variables, functions, history, location; the document also comes under the window and can be considered as the property of the window.
What is the difference between innerHTML and innerText?
innerHTML will process an HTML tag if found in a string, whereas innerText will not. For Example document.querySelector('p').innerHTML='one <br> two' gives the output one and two in two lines as <br> in html is a new line. Whereas document.querySelector('p').innerText='one <br> two' gives the output of the text as it is in one line.
Consider the code snippet below. What will the console output be and why?
(function(x) {
return (function(y) {
console.log(x);
})(2)
})(1);
The output will be 1, even though the value of x is never set in the inner function. Here’s why:
As explained in our JavaScript Hiring Guide, a closure is a function, along with all variables or functions that were in-scope at the time that the closure was created. In JavaScript, a closure is implemented as an “inner function”; i.e., a function defined within the body of another function. An important feature of closures is that an inner function still has access to the outer function’s variables.
Therefore, in this example, since x is not defined in the inner function, the scope of the outer function is searched for a defined variable x, which is found to have a value of 1.
What will the following code output to the console and why:
var hero = {
_name: 'John Doe',
getSecretIdentity: function (){
return this._name;
}
};
var stoleSecretIdentity = hero.getSecretIdentity;
console.log(stoleSecretIdentity());
console.log(hero.getSecretIdentity());
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
}
}
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.
How many types of triggers are present in update panel?
There are two types of triggers used in update panel:
PostBackTrigger – This works as full postback and it cannot work asynchronously
AsyncPostBackTrigger – Partial post back asynchronously
What are all the controls of Ajax?
Following are the controls of Ajax:
ScriptManager
ScriptManagerProxy
UpdatePanel
UpdateProgress
Timer
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.
The keyword ‘this’ refers to the current instance of the object when used inside a function. But, when used outside a function, it refers to the window object.
Is Exception handling possible in Javascript?
With the latest version of Javascript, exception handling is possible; and this can be achieved using the following keywords try, catch and finally.
How is it possible to get the total number of arguments that are passed to a function?
The arguments.length property helps in getting the total number of arguments that are passed to a function.
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| NetApp Most Frequently Asked Latest JavaScript Interview Questions Answers |
What is the difference between typeof and instanceof operators in Javascript?
The typeof operator returns a string of what type the operand is. Whereas, the instanceof operator does not work with primitive data types; but works with objects and checks on what type the object is.
What is DOM?
DOM (Document Object Model) is an object-oriented representation of the HTML elements. All the elements (or nodes) are part of window.document.
Expand BOM and explain it.
BOM stands for Browser Object Model. Using BOM interaction with a browser is possible. Default object of the browser is a window.
What is the difference between window and document in Javascript?
Javascript window is a global object which holds variables, functions, history, location; the document also comes under the window and can be considered as the property of the window.
What is the difference between innerHTML and innerText?
innerHTML will process an HTML tag if found in a string, whereas innerText will not. For Example document.querySelector('p').innerHTML='one <br> two' gives the output one and two in two lines as <br> in html is a new line. Whereas document.querySelector('p').innerText='one <br> two' gives the output of the text as it is in one line.
Consider the code snippet below. What will the console output be and why?
(function(x) {
return (function(y) {
console.log(x);
})(2)
})(1);
The output will be 1, even though the value of x is never set in the inner function. Here’s why:
As explained in our JavaScript Hiring Guide, a closure is a function, along with all variables or functions that were in-scope at the time that the closure was created. In JavaScript, a closure is implemented as an “inner function”; i.e., a function defined within the body of another function. An important feature of closures is that an inner function still has access to the outer function’s variables.
Therefore, in this example, since x is not defined in the inner function, the scope of the outer function is searched for a defined variable x, which is found to have a value of 1.
What will the following code output to the console and why:
var hero = {
_name: 'John Doe',
getSecretIdentity: function (){
return this._name;
}
};
var stoleSecretIdentity = hero.getSecretIdentity;
console.log(stoleSecretIdentity());
console.log(hero.getSecretIdentity());
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
}
}
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.