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 the difference between RegisterClientScriptBlock, RegisterClientScriptInclude and RegisterClientScriptResource?
Following are the functions:
RegisterClientScriptBlock – The script is specified as a string parameter.
RegisterClientScriptInclude – By setting the source attribute to a URL that point to a script file.
RegisterClientScriptResource – specifies Resource name in an assembly. The source attribute is automatically populated with a URL by a call to an HTTP handler that retrieves the named script from the assembly.
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 the difference between RegisterClientScriptBlock, RegisterClientScriptInclude and RegisterClientScriptResource?
Following are the functions:
RegisterClientScriptBlock – The script is specified as a string parameter.
RegisterClientScriptInclude – By setting the source attribute to a URL that point to a script file.
RegisterClientScriptResource – specifies Resource name in an assembly. The source attribute is automatically populated with a URL by a call to an HTTP handler that retrieves the named script from the assembly.
 |
| Zensar Technologies JavaScript Most Frequently Asked Latest Interview Questions Answers |
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().
What will the code below output to the console and why?
(function(){
var a = b = 3;
})();
console.log("a defined? " + (typeof a !== 'undefined'));
console.log("b defined? " + (typeof b !== 'undefined'));
Since both a and b are defined within the enclosing scope of the function, and since the line they are on begins with the var keyword, most JavaScript developers would expect typeof a and typeof b to both be undefined in the above example.
However, that is not the case. The issue here is that most developers incorrectly understand the statement var a = b = 3; to be shorthand for:
var b = 3;
var a = b;
But in fact, var a = b = 3; is actually shorthand for:
b = 3;
var a = b;
As a result (if you are not using strict mode), the output of the code snippet would be:
a defined? false
b defined? true
But how can b be defined outside of the scope of the enclosing function? Well, since the statement var a = b = 3; is shorthand for the statements b = 3; and var a = b;, b ends up being a global variable (since it is not preceded by the var keyword) and is therefore still in scope even outside of the enclosing function.
Note that, in strict mode (i.e., with use strict), the statement var a = b = 3; will generate a runtime error of ReferenceError: b is not defined, thereby avoiding any headfakes/bugs that might othewise result. (Yet another prime example of why you should use use strict as a matter of course in your code!)
What is the significance of, and reason for, wrapping the entire content of a JavaScript source file in a function block?
This is an increasingly common practice, employed by many popular JavaScript libraries (jQuery, Node.js, etc.). This technique creates a closure around the entire contents of the file which, perhaps most importantly, creates a private namespace and thereby helps avoid potential name clashes between different JavaScript modules and libraries.
Another feature of this technique is to allow for an easily referenceable (presumably shorter) alias for a global variable. This is often used, for example, in jQuery plugins. jQuery allows you to disable the $ reference to the jQuery namespace, using jQuery.noConflict(). If this has been done, your code can still use $ employing this closure technique, as follows:
(function($) { /* jQuery plugin code referencing $ */ } )(jQuery);
What is the significance, and what are the benefits, of including 'use strict' at the beginning of a JavaScript source file?
The short and most important answer here is that use strict is a way to voluntarily enforce stricter parsing and error handling on your JavaScript code at runtime. Code errors that would otherwise have been ignored or would have failed silently will now generate errors or throw exceptions. In general, it is a good practice.
Some of the key benefits of strict mode include:
Makes debugging easier. Code errors that would otherwise have been ignored or would have failed silently will now generate errors or throw exceptions, alerting you sooner to problems in your code and directing you more quickly to their source.
Prevents accidental globals. Without strict mode, assigning a value to an undeclared variable automatically creates a global variable with that name. This is one of the most common errors in JavaScript. In strict mode, attempting to do so throws an error.
Eliminates this coercion. Without strict mode, a reference to a this value of null or undefined is automatically coerced to the global. This can cause many headfakes and pull-out-your-hair kind of bugs. In strict mode, referencing a a this value of null or undefined throws an error.
Disallows duplicate parameter values. Strict mode throws an error when it detects a duplicate named argument for a function (e.g., function foo(val1, val2, val1){}), thereby catching what is almost certainly a bug in your code that you might otherwise have wasted lots of time tracking down.
Note: It used to be (in ECMAScript 5) that strict mode would disallow duplicate property names (e.g. var object = {foo: "bar", foo: "baz"};) but as of ECMAScript 2015 this is no longer the case.
Makes eval() safer. There are some differences in the way eval() behaves in strict mode and in non-strict mode. Most significantly, in strict mode, variables and functions declared inside of an eval() statement are not created in the containing scope (they are created in the containing scope in non-strict mode, which can also be a common source of problems).
Throws error on invalid usage of delete. The delete operator (used to remove properties from objects) cannot be used on non-configurable properties of the object. Non-strict code will fail silently when an attempt is made to delete a non-configurable property, whereas strict mode will throw an error in such a case.
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().
What will the code below output to the console and why?
(function(){
var a = b = 3;
})();
console.log("a defined? " + (typeof a !== 'undefined'));
console.log("b defined? " + (typeof b !== 'undefined'));
Since both a and b are defined within the enclosing scope of the function, and since the line they are on begins with the var keyword, most JavaScript developers would expect typeof a and typeof b to both be undefined in the above example.
However, that is not the case. The issue here is that most developers incorrectly understand the statement var a = b = 3; to be shorthand for:
var b = 3;
var a = b;
But in fact, var a = b = 3; is actually shorthand for:
b = 3;
var a = b;
As a result (if you are not using strict mode), the output of the code snippet would be:
a defined? false
b defined? true
But how can b be defined outside of the scope of the enclosing function? Well, since the statement var a = b = 3; is shorthand for the statements b = 3; and var a = b;, b ends up being a global variable (since it is not preceded by the var keyword) and is therefore still in scope even outside of the enclosing function.
Note that, in strict mode (i.e., with use strict), the statement var a = b = 3; will generate a runtime error of ReferenceError: b is not defined, thereby avoiding any headfakes/bugs that might othewise result. (Yet another prime example of why you should use use strict as a matter of course in your code!)
What is the significance of, and reason for, wrapping the entire content of a JavaScript source file in a function block?
This is an increasingly common practice, employed by many popular JavaScript libraries (jQuery, Node.js, etc.). This technique creates a closure around the entire contents of the file which, perhaps most importantly, creates a private namespace and thereby helps avoid potential name clashes between different JavaScript modules and libraries.
Another feature of this technique is to allow for an easily referenceable (presumably shorter) alias for a global variable. This is often used, for example, in jQuery plugins. jQuery allows you to disable the $ reference to the jQuery namespace, using jQuery.noConflict(). If this has been done, your code can still use $ employing this closure technique, as follows:
(function($) { /* jQuery plugin code referencing $ */ } )(jQuery);
What is the significance, and what are the benefits, of including 'use strict' at the beginning of a JavaScript source file?
The short and most important answer here is that use strict is a way to voluntarily enforce stricter parsing and error handling on your JavaScript code at runtime. Code errors that would otherwise have been ignored or would have failed silently will now generate errors or throw exceptions. In general, it is a good practice.
Some of the key benefits of strict mode include:
Makes debugging easier. Code errors that would otherwise have been ignored or would have failed silently will now generate errors or throw exceptions, alerting you sooner to problems in your code and directing you more quickly to their source.
Prevents accidental globals. Without strict mode, assigning a value to an undeclared variable automatically creates a global variable with that name. This is one of the most common errors in JavaScript. In strict mode, attempting to do so throws an error.
Eliminates this coercion. Without strict mode, a reference to a this value of null or undefined is automatically coerced to the global. This can cause many headfakes and pull-out-your-hair kind of bugs. In strict mode, referencing a a this value of null or undefined throws an error.
Disallows duplicate parameter values. Strict mode throws an error when it detects a duplicate named argument for a function (e.g., function foo(val1, val2, val1){}), thereby catching what is almost certainly a bug in your code that you might otherwise have wasted lots of time tracking down.
Note: It used to be (in ECMAScript 5) that strict mode would disallow duplicate property names (e.g. var object = {foo: "bar", foo: "baz"};) but as of ECMAScript 2015 this is no longer the case.
Makes eval() safer. There are some differences in the way eval() behaves in strict mode and in non-strict mode. Most significantly, in strict mode, variables and functions declared inside of an eval() statement are not created in the containing scope (they are created in the containing scope in non-strict mode, which can also be a common source of problems).
Throws error on invalid usage of delete. The delete operator (used to remove properties from objects) cannot be used on non-configurable properties of the object. Non-strict code will fail silently when an attempt is made to delete a non-configurable property, whereas strict mode will throw an error in such a case.
Post a Comment