Web Technology Experts Notes

Monday, 4 April 2016

Javascript Interview Questions And Answers for 3 year experienced

Question: How to open a URL in a new tab using javaScript?
JavaScript

function OpenInNewTab() {  
  var url='http://www.onlinevideoswatch.com/';
  var win = window.open(url, '_blank');
  win.focus();
}

Html

<div onclick="OpenInNewTab();">
Click to Open in Tab</div>

Question: How to Convert JavaScript String to be all lower case?

var strVal="How are yOu";
strVal.toLowerCase(); //how are you

Question: How to detect a mobile device in javaScript?

if( /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {
 /** You are using Mobile Devices**/
}

Question: How do you check if a variable is an array in JavaScript?

var myArray=new Array('one','two','three','four');
console.log(myArray);
var myval='two';

if (myArray.indexOf(myval)) {
  console.log('value is Array!');
} else {
  console.log('Not an array');
}

Question: How to generate random number between two numbers (1-100)?

var minimum=1
var maximum=100
var randomnumber 

randomnumber = Math.floor(Math.random() * (maximum - minimum + 1)) + minimum;
console.log(randomnumber);

Question: How to declare constant in javaScript?

const MY_CONSTANT_NAME = "value that will never change";

Here you can't change the value of "MY_CONSTANT_NAME"
It Will work in all browsers except IE 8, 9 and 10.

Question: How can I format numbers as money format?

var monthlyExpanse=98765.432
monthlyExpanse.toFixed(4);//98765.4320 
monthlyExpanse.toFixed(3);//98765.432 
monthlyExpanse.toFixed(2);//98765.43
monthlyExpanse.toFixed(1);//98765.4

Question: How can display JSON data in readble form?

var str = JSON.stringify(obj, null, 2); // space level  2

Question: How to Get selected value from dropdown list ?
HTML

<select id="countryId">  
  <option value="11">England</option>
<option selected="selected" value="22">India</option>
  <option value="33">Japan</option>
</select>

JavaScript

var e = document.getElementById("countryId");
var countryId = e.options[e.selectedIndex].value;
//console.log(countryId); //22

Question: How to convert a number to hexadecimal,octal ?

var myNumber= 500;
//console.log(myNumber.toString(16));//1f4
//console.log(myNumber.toString(8));//764

Question: How to convert a hexadecimal,octal number to decimal?

var hexaDecimal='1f4';
var octal='764';
console.log(parseInt(hexaDecimal,16)); //500
console.log(parseInt(octal,8)); //500

Question: How to convert a String to Decimal?

var strVal='100';
number=parseInt(strVal);

Question: What is use of instanceof?

var simpleStr = "This is string"; 
var myString  = new String();
var newStr    = new String("constructor");
var myDate    = new Date();
var myObj     = {};

simpleStr instanceof String; // returns false, checks the prototype chain, finds undefined
myString  instanceof String; // returns true
newStr    instanceof String; // returns true
myString  instanceof Object; // returns true

Question: How to Scroll to the top of the page?

var xCoord=200;
var yCoord=500;
window.scrollTo(xCoord, yCoord);

Question: How to display javaScript Object?

console.log(obj);

Question: How to use namespaces in javaScript?

var myNamespaceName = {

    foo: function() {
        alert('foo');
    },

    foo2: function() {
        alert('foo2');
    }
};

myNamespaceName.foo();//alert foo
myNamespaceName.foo2();//alert foo2

Friday, 1 April 2016

Ajax Interview Questions and Answers for Fresher

Question: What are the advantages of AJAX?

Quick Response.
Quick Response without loading page.
Save the Bandwidth
Client Server Interaction what user letting know (User will not get disturb)

Question: What are the dis Advantages of AJAX?

Dependency on JavaScript.
An simple js error, Ajax will not called.
Security issues Might comes, if not implemented securely.
Difficult in Debugging for beginner
Sometimes browser compatibility issues comes.

Question: What are top website, who uses Ajax?

Youtube
Google
Bing
Gmail
Twitter
Linkdin

Question: What are security issues in AJAX?

Ajax is visible in browser console
Request, Response, header and cookie are visiable in browser console.
Every time called ajax is purely visiable in Ajax
An Ajax request can be called by hackers OR unauthorized, It can damage the website if there are not properly security checks
Attackers can try the ajax call with different request parameter.

Question: What are the technologies used by AJAX?

Javascript
XMLHttpRequest
XML/JSON/HTML
DOM
You can also use third party libaraies like jQuery, mootools etc

Question: What are common AJAX Framework?

jQuery
MooTools
Prototype
YUI
Dojo Toolkit
Google Web Toolkit (GWT)

Question:What are Ajax applications?
The web applicable which use the more ajax calls are ajax application.

Question: What are different stage of XMLHttpRequest?

0: request not initialized
1: server connection established
2: request received
3: processing request
4: request finished and response is ready

Question: In Ajax call, which method is more secure GET/Post?
POST is more secure as compare to Get Method.

Question: Can anyone send ajax request with POST Method ?
Yes, can send using CURL.

Question: What is the difference between JavaScript and AJAX? JavaScript an object-oriented computer programming language used in web browsers.
Ajax is set of web development techniques using JavaScript to send/receive the data from server without loading page.

Question: What is Asynchronous in Ajax?
We can set the Asynchronous value as true OR false.

Async=true

Ajax request execute independently, Its response can come earlier than other request which is execute later .

Async=false

Ajax request does not execute independently, Its response can comes when earlier request finished.

Question: How to submit entire form data with Ajax?

//serialize ajax Data
var formData = $('form#formId').serialize();
$.ajax({ 
        url: '/my/site',
         data: formData,
         type: 'post',
         success: function(result) {
                      console.log(result);
          }
});

Question:Give a simple example of JSONP with Ajax?

$.getJSON("http://twitter.com/status/user_timeline/padraicb.json?count=10&callback=?", function(result){
   //Now result have response of ajax call
   console.log(result);
});