var object  = {
    a : 50,
    b: 60
}
var x = JSON.parse(JSON.stringify(object));
console.log(x);

// timer methods from web API 

setTimeout(function(){
    console.log('after 5 sec');
}, 5000);

var xhr = new XMLHttpRequest();
xhr.onreadystatechange =  function(){
    if(this.readyState == 4){
        clearTimeout(timeout);
    }
}
var timeout = setTimeout (function(){
     xhr.abort(); 
}, 2000);

xhr.open('GET', url, true);
xhr.send();
 
//----------------------------------------------//

function hello(a,b) {
    return a+b;
}

function add(a){
    return function(b){
        return function(c){
              return a+b+c;
        }
    }
}
add(4)(5)(8);

var x = add(4);
var y = x(5);
var z = y(8);

/************************************************* */

var keywords = ["do","if","else","for" ,"switch"];

keywords
    .filter( i =>  i.length > 3 )
    .map(    i =>  i.concat('Hi') )
    .sort( (a,b) => a < b ? -1 : 1);

/************************************************ */

class ChainAble {
  firstMethod() {
    console.log('This is the First Method');
    return this;
  }
  
  secondMethod() {
    console.log('This is the Second Method');
    return this;
  }
  
  thirdMethod() {
    console.log('This is the Third Method');
    return this;
  }
}

const chainableInstance = new Chainable()
chainableInstance
  .firstMethod()
  .secondMethod()
  .thirdMethod();
  
  /**************************************************** */

var sayHello = function ({name, surname}){
    console.log(`hello ${name} ${surname}`); 
}
var sayHello2 = function ({name = "tarun", surname = "sharma"}, times){
    console.log(`hello ${name} ${surname} ${times}`); 
}

sayHello({name : 'tks'});
sayHello();
sayHello(566);


var x = {};

Object.defineProperty(x,'readOnly' , {
     value : 56,
     writable : false,
     enumerable : true,
     configurable : false
})
Object.getOwnPropertyDescriptor(x, 'readOnly');
console.log(x);

//-------------------------------------------------------------------//
// remove duplicates from Array 

var array = [4,5,6,7,8,8,6,7,8];

array.filter(function(item, index, array){
     return array.indexOf(item) === index
});

var x = [... new Set(array)];
Array.from(new Set(array));


var object = {
    a : 70,
    b : 70,
    c : {
        a :80
    } 
};


function duplicate(err){
    var hashTable = {};
    return arra.filter(function(el){
        var key = JSON.stringify(el);
        var match = Boolean(hashTable[key]);
        
        return (match ? false : hashTable[key] = true);
    })
}
var array = [
    { a :1},
    {a :1 },
    [1,2],
    [1,2]
]
duplicate(array);


/************************************************************ */
//Flatten an Array
var myarray = [ [1,2], [4,5,6,7],[6,7,8,9]];