Web Technology Experts Notes

Showing posts with label JavaScript. Show all posts

Sunday 17 January 2016

How to load disqus when scroll to the bottom of the page?

Question: What is Disqus?
It is comment hosting service for web sites and online communities. It provide Services so that you can add comment system in your website.

Question: is Disqus multilingual?
Yes, It is.

Question: When Disqus was Launched?
October 2007

Question: Can we embed disqus in website?
Yes, you can embed.

Question: Does it provides channel for discussion?
Yes, It provides channel to discuss.

Question: What is offical website of Disqus?
http://disqus.com

Question: Can facebook user post comment using their fb account?
Yes, Facebook, twitter and google user can post comment using their account

Question: How to load disqus when scroll to the bottom of the page?

                        
  /*  CONFIGURATION VARIABLES  - MUST SET */
  var disqus_developer = 0;
  var disqus_shortname = 'aboutcity'; // required: replace example with your forum shortname                            
  var disqus_identifier = '/2015/07/ajax-technical-interview-questions-and-answers-for-experienced.html';
  var disqus_url = 'http://www.web-technology-experts-notes.in/2015/07/ajax-technical-interview-questions-and-answers-for-experienced.html';                    
  /*  CONFIGURATION VARIABLES  - MUST SET */
  
  var disqus_loaded = false;

  function load_disqus(){     
    disqus_loaded = true;
    var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true;
    dsq.src = "http://"+disqus_shortname+".disqus.com/embed.js";       
    (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq);

  }

/** check now bottom of page **/
  window.onscroll = function(e) {
   if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
    //hit bottom of page
    if (disqus_loaded==false){ load_disqus() };
   }
  };

Thursday 13 August 2015

How do you get a timestamp in JavaScript?

Question: What is timestamp?
A timestamp is the current time of an event that is recorded by a computer. In JavaScript, it gives local time (computer ).

Question: How do you get a timestamp in JavaScript?

Date.now()

Question: How do you get a timestamp in number of seconds?

Math.floor(Date.now() / 1000)

Question: How do handle exception to this is IE8 and other Browser?


if (!Date.now) {
Date.now()
}

Question: How do you get the date from the time object

new Date().getDate()

Question: What are other date-functions in javascript?
getDate(): Get the day as a number (1-31)
getDay(): Get the weekday as a number (0-6)
getFullYear(): Get the four digit year (yyyy)
getHours(): Get the hour (0-23)
getMilliseconds(): Get the milliseconds (0-999)
getMinutes(): Get the minutes (0-59)
getMonth(): Get the month (0-11)
getSeconds(): Get the seconds (0-59)
getTime(): Get the time (milliseconds since January 1, 1970)

Wednesday 12 August 2015

How do closures work in Javascript

Question: What is closures?
Whenever you defined a the function within another function, the inner function has access to variables in the outer function.

Following are Simple example of closure.

function mainFunction(outerData) {
  var mainFuncData = 3;

  function innerFunction(innerFuncData) {
    console.log(outerData + innerFuncData + (++mainFuncData)); // will alert 16
  }

  innerFunction(10);
}

mainFunction(7); //17

Question: Why it can access to variables in the outer function?
Because It is defined as var , which means it is global variable.

Sunday 7 June 2015

Load multiple javascript files asynchronously

In Every website, We have to include the JavaScript. We need to include multiple JavaScript file in single web page.

It's always prefer to include the javascript at the bottom of the page so that loading of content remain fast. So we should add at the bottom of the page.

We should also load the JavaScript files asynchronously, means load JavaScript file parallel.

There are two ways to load JavaScript file. Newer browsers have async attribute which load JavaScript asynchronously.
<scritp async="true" src="yourscript.js" type="text/javascript"></scritp>

Use custom JavaScript function to load javascript-file asynchronously.

<script type="text/javascript">
function loadScript (scriptpath){
    var s=document.getElementsByTagName('script')[0];
    var ss=document.createElement('script');
    ss.type='text/javascript';
    ss.async=true;
    ss.src= scriptpath;
    s.parentNode.insertBefore(ss,s);
}
</script>

Just call the loadScript function to load javascript file asynchronously. For Example.

<script type="text/javascript">
loadScript('/js/jQueryJSFIle1.js');
loadScript('/js/jQueryJSFIle2.js');
loadScript('/js/jQueryJSFIle3.js');
</script>

Thursday 2 April 2015

Javascript Interview Questions and Answers for Experienced 2

Question: How to set a default parameter value for a JavaScript function?

/** Here email is parameter in which we have set the default value i.e email@domain.com **/
function function1(name, email)
 {
   email = typeof email !== 'undefined' ? email : 'defaultemail@domain.com';
    console.log('name='+name+', Email= '+email);
 }

function1('john','myname@gmail.com');
function1('john');

Queston: How to convert a string to lowercase?

var str='This is testing String';
str = str.toLowerCase();
console.log(str);

Question: How to modify the URL of page without reloading the page?
use pushState javascript function.
For Example:

window.history.pushState('page2', 'This is page Title', '/newpage.php');

Question: How to convert JSON Object to String?

var myobject=['Web','Technology','Experts','Notes']
JSON.stringify(myobject);

Question: How to convert JSON String to Object?

var jsonData = '{"name":"web technology","year":2015}';
var myobject = JSON.parse(jsonData);
console.log(myobject);

Question: How to check an variable is Object OR String OR Array?
Use below function to get Data type of javascript variable.

function checkDataType(someVar){
 result ='String';
    if(someVar instanceof Object){
       result ='Object'
    }
    if($.isArray(someVar)){
      result = 'Array';
    }
return result;
}

var someVar= new Array("Saab", "Volvo", "BMW");
console.log(result);

Question: Can i declare a variable as CONSTANT like in PHP?
No, I think cosntant not exist in javascript.
But you can follow same type convention to declare constant.

var CONSTANT_NAME = "constant value";

Question: How to open URL in new tab in javascript?
use javascript, window.open function.

window.open('http://www.web-technology-experts-notes.in/','_blank');

Question: What is difference between undefined and object?
undefined means some variable's value is not defined yet.
object means variables's value is defined that is either function, object OR array.

With use of below, you can easily determine whether it is object OR NULL.

console.log(typeof(null));      // object
console.log(typeof(undefined)); // undefined

Question: How to get current date in JavaScript?

var today = new Date();
console.log(today);

Question: How do I declare a namespace in JavaScript?

var myNamespace = {

    function1: function() {   },

    function2: function() {    }

    function3: function() {    }
};

myNamespace.function3();

Question: What is the best way to detect a mobile device in jQuery?

if( /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {

}

Question: How to detect mobiles including ipad using navigator.useragent in javascript?

 if(navigator.userAgent.match(/Android/i) || navigator.userAgent.match(/webOS/i) ||  navigator.userAgent.match(/BlackBerry/i) || navigator.userAgent.match(/iPhone/i)){
        console.log('Calling from Mobile');      
    }else{
    console.log('Calling from Web');      
}

Question: How to detect mobiles including ipad using navigator.useragent in javascript?

 if(navigator.userAgent.match(/Android/i) || navigator.userAgent.match(/webOS/i) ||  navigator.userAgent.match(/BlackBerry/i) || navigator.userAgent.match(/iPhone/i)){
        console.log('Calling from Mobile');      
    }else{
    console.log('Calling from Web');      
}