October 12, 2018

Sreekanth B

Amazon JavaScript Most Frequently Asked Latest Interview Questions Answers

What is the use of each function in jQuery?

Each function is used to iterate each and every element of an object. It is used to loop DOM elements, arrays and the object properties.

What is the difference between size and length of jQuery?

Size and length both returns the number of element in an object. But length is faster than the size because length is a property and size is a method.

Can we add more than one ‘document.ready’ function in a page?

Yes, we can add more than one document.ready function in a page. But, body.onload can be added once in a page.

What is the use of jQuery load method?

jQuery load method is a powerful AJAX method which is used to load the data from a server and assign the data into the element without loading the page.

Whether our own specific characters are used in place of $ in jQuery?

Yes, We can use our own variable in place of $ by using the method called no Conflict () method.

var sample = $.noConflict()
Amazon JavaScript Most Frequently Asked Latest Interview Questions Answers
Amazon JavaScript Most Frequently Asked Latest Interview Questions Answers

What are the four parameters used for jQuery Ajax method?

The four parameters are

URL – Need to specify the URL to send the request
type – Specifies type of request(Get or Post)
data – Specifies data to be sent to server
Cache – Whether the browser should cache the requested page.

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.

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 are the components of the ASP.NET AJAX architecture?

There are two components of AJAX Architecture:

AJAX client architecture
AJAX server architecture

What are the extender controls?

The extender controls uses a block of JavaScript code to add new and enhanced capabilities to ASP.NET.

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