Web Technology Experts Notes

Wednesday, 6 April 2016

Javascript Questions And Answers for Fresher and Experienced

Question: How to pass multiple parameter in setTimeout function?

function myFunctionName(var1,var2){
    console.log('called after 2 sec of page load '+var1+' '+var2);
}
setTimeout(myFunctionName,2000,'value1','value2');

Question: How to enumerate the properties of js objects?

var myObject = {name1: 'Value1',name2: 'Value2'};
//console.log(myObject); //It will print all the values

for (var name in myObject) {
  //console.log(name+'=>'+myObject[name]);
  }

Question: How to measure the execution time of javascript script?

var startTime = new Date().getTime();
/*
Write here you script
*/
for(i=1;i<=500000; i++){
}
var endTime = new Date().getTime();

var time = endTime - startTime;
console.log('Execution time in Milli Seconds: ' + time);
console.log('Execution time in Seconds: ' + time/1000);

Question: How to listen (Do some changes) the window.location.hash change?

$(window).on('hashchange', function() {  
  callNewFunction(window.location.href)  
});
function callNewFunction(url){
    console.log('Hash URL is called');
}

After appling above code, whenever you add/update the hash value, callNewFunction will called automatically.

hashchange event is HTML5 feature and supported by all modern browsers and support is added in following browser.

Internet Explorer 8
Firefox 3.6
Chrome 5
Safari 5
Opera 10.6

Question: How to add class in an element?
HTML Part

<div id="myDivId">
</div>

javaScript Part

var d = document.getElementById("myDivId");
d.className += " newClass";

Question: How to get the list of classes for an element?

d = document.getElementById("myDivId");
console.log(d.className);

Question: Can we compare two javaScript objects?
Yes, We can compare two javascript objects. See Following examples.

var myObject1 = {name1: 'Value1',name2: 'Value2'};
var myObject2 = {name1: 'Value111',name2: 'Value222'};
if(JSON.stringify(myObject1) === JSON.stringify(myObject2)){
 console.log("Both object are same");
}else{
console.log("Both object are different");
}

Question: What is difference between Array(3) and Array('3') in javascript?
new Array(3), means declare the 3 elements and each have value "undefined". new Array('3'), means declare the 1 element and have value 3.

console.log(new Array(3)); // [undefined, undefined, undefined]
console.log(new Array('3')); // ["3"]

Question: How to get browser URL for all browser?

console.log(window.location.href);

Question: How to remove an element(string OR object ) from javascript Array/Object?

var myObject = {name1: 'Value1',name2: 'Value2'};
delete myObject['name1']
console.log(myObject);

Question: What does jQuery.fn mean?
jQuery.fn is just an prototype for defining the new functions.
fn is an alias to the prototype property.
For Example,

$.fn.newFunctionName = function(val){
console.log('something '+val); //something Test Value
};
$.fn.newFunctionName('Test Value');

Question: How to remove an empty elements from an Array?

var simpleArray = [1,3,,3,null,,0,,undefined,4,,6,,];
var cleanArray = simpleArray.filter(function(n){ return n != undefined }); 
console.log(cleanArray);

Question: How to add 5 days in JavaScript?

var result = new Date();
result.setDate(result.getDate() + 5);
console.log(result);

Tuesday, 5 April 2016

Javascript Interview Questions And Answers for 4 year experienced

Question: How to remove an item from javaScript Array?

var myArray = new Array('a', 'b', 'c', 'd');
var index = myArray.indexOf('b');
myArray.splice(myArray, 1);
console.log(myArray);

Question: How to call a function after 2 section?

function myFunctionName(){
    //console.log('called after 2 sec of page load');
}
setTimeout(myFunctionName,2000);

Question: How to start/stop setInterval function?

function myFunctionName(){
    //console.log('called after 2 sec of page load');
}
var refreshIntervalObject =setInterval(myFunctionName, 3000);
clearInterval(refreshIntervalObject);

Question: What is basic difference between $(document).ready() and window.onload?
$(document).ready(): This event occurs after the HTML document has been loaded.
window.onload This event when all content (e.g. html, js, images) also has been loaded.

Question: Is JavaScript a pass-by-reference OR pass-by-value?
passed by reference

Question: How to send cross domain Ajax Request?
You can send ajax request with "JSONP" only in Cross Domain.

$.ajax({
    url: '/ajax',
    dataType: 'jsonp',
    success:function(data, textStatus, request){
      console.log(request.getResponseHeader('some_header'));
    
    }
});

Question: What is CDATA? When it is required?
CDATA stand for "Character Data" and it means that the data in between tags.
CDATA is required when you need an document to parse as XML.

Question: How to compare two Dates in javaScript?

var date1 = new Date();
var date2 = new Date(d1);
if(d1.getTime() === d2.getTime()){
    /* Both Time are are Same **/
}else{
    /* Time are are Different**/
}

Question: How to merge two array?

var array1 = ["One","Two"];
var array2 = ["Three", "Four"];
var mergeArray = array1.concat(array2);
console.log(mergeArray);

Question: How to use Regular Expression in JavaScript?

var searchString= '12 34';
var result=searchString.match( /\d+/g ) 
console.log(result ); //["12", "34"]
console.log(result.length+' Elements matched'); //2 Elements matched

Question: How to trigger ENTER key was pressed?
var code = e.keyCode || e.which; if(code == 13) { /** Enter key is pressed **/ }

Question: How to select element by Name?

var arrChkBox = document.getElementsByName("elementName");

Question: How to Convert character to ASCII code in JavaScript?

var characterString='$';
characterString.charCodeAt(0);//36

Question: What do you mean by "javascript:void(0)"?
javascript:void(0) means "DO Nothing";
for example:

<a href="javascript:void(0)">No effect on clicking</a>

Question: Can we detect, if javaScript is enabled?
Yes, we can do with html tag.

<noscript>
    javascript is not enabled, Please enable javascript in your browser.
</noscript>

Question: How to add element in the begining OR at the end of array?

var myArray = new Array('a', 'b', 'c', 'd');
myArray.push('end');
myArray.unshift('start');
console.log(myArray);

Wednesday, 6 April 2016

Javascript Questions And Answers for Fresher and Experienced

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Tuesday, 5 April 2016

Javascript Interview Questions And Answers for 4 year experienced

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