Example

Example:1
for (var i = 0; i < 5; i++) {
  (function(x) {
    setTimeout(function() { console.log(x); }, x * 1000 );
  })(i);
}

Example:2
var x = 21;
var girl = function () {
  console.log(x);
  var x = 20;
};
girl (); // undefined

Example:3
function x (callBack){
   setTimeout(()=>{
      const p = "hello"
      callBack(p)
   },2000)
}
x(function(res){ console.log(res)})

Example:4
function cP(successCb,errorCb){
    setTimeout(()=>{
       let data ="ajay";
       if(data){
          successCb(data)
       } else{
          errorCb("no Data")
       }
    },2000)
}
cP((res)=>{console.log(res)},(er)=>{console.log(er)})

Example:5
var MySingleTon = (function(){
  var instance;
  var data =[];
  var add = function(item){
     data.push(item)
  }
  var getData = function(){
    return data;
  }
  var createInstance = function(){
    return {
       Add:add,
       GetData:getData
    }
  }
return {
    getInstance: function(){
       return instance || (instance= createInstance());
   }
}
}());
var myModule = MySingleTon.getInstance();

Example:6
function Person(name) {
    console.log(this) //Window {parent: Window, opener: null, top:  Window, length: 4, frames: Window, …}
    this.name = name;
    this.sayName = function() {
        console.log(this.name);
    };
}
Person('Johan')
.....................................................
function Person(name) {
    console.log(this)
    this.name = name;
    this.sayName = function() {
        console.log(this);
    };
}
var person1 = new Person("Nicholas");
var person2 = new Person("Greg");
person1.sayName() // Person {name: "Nicholas", sayName: ƒ}

function x(input){
  if(input.includes('_')){
      var a = input.split("_");
      str = ''
      for(i = 0; i< a.length; i++){
          if(i == 0){
            str+=a[i]
          } else {
              str+=a[i] && a[i].slice(0,1).toUpperCase();
              str+=a[i] && a[i].slice(1)
          }
      } 
  }  else {
       var a = input.split("");
       str = '';
       a.forEach((x)=>{
           if(x.toUpperCase() == x){
              str +='_'+x.toLowerCase();  
           } else{
                str +=x;  
           }
       })
  }
  return str;
}
x("ajayKumaMah")

function x(input){
  var a = input.split("");
  if(input.includes('_')){
      str = '';
      var chk = 0;
       a.forEach((x,i)=>{
           if(x == '_'){
             chk = 1;
           } else{
                if(chk == 1) {
                  str +=x.toUpperCase();  
                  chk = 0
                } else {
                     str +=x  
                }
           }
       })
  }  else {       
       str = '';
       a.forEach((x)=>{
           if(x.toUpperCase() == x){
              str +='_'+x.toLowerCase();  
           } else{
                str +=x;  
           }
       })
  }
  return str;
}
x("ajay_kumar_mah")

/Create an object
function icreon (){} // constructon 1
var icreon = {} // literal 2
//Object.create Create a new object with the prototype set to a certain object
var cat ={
makeSound: function(){
console.log(this.sound)
}
}
var mark = Object.create(cat)
mark.sound = 'meyau';
//mark.makeSound();
var dog = Object.create(cat)
dog.sound = 'bho Bho';
//dog.makeSound();
function Animal(name) {
this.name = name;
}
Animal.prototype = {
canWalk: true,
sit: function() {
this.canWalk = false
console.log(this.name + ' sits down.')
}
}
function ss (a){
Animal.call(this, a);
}
ss.prototype = Object.create(Animal.prototype);
//var a = new Animal('dog');
var b = new ss('hi')
//console.log(b.sit())
// es5
function Bird (weight, height){
this.w = weight;
this.h = height;
}
Bird.prototype.Walk = function() {
console.log('walk')
}
function penguin (weight, height){
Bird.call(this, weight, height)
}
penguin.prototype = Object.create(Bird.prototype);
//penguin.prototype.constructor = penguin;
penguin.prototype.swim = function(){
console.log('swim')
}
var a = new penguin(10,20);
a.swim();
a.Walk();
//es6
class shap{
constructor(red, green){
this.red = red;
this.green = green;
}
DrawShap (a){
console.log('this is ' + this.red +' '+ a)
}
}
class shapwork extends shap {
constructor(a,b){
super(a,b);
}
workShap (){
console.log(this.red)
}
}
s = new shapwork('red', 'green3')
s.DrawShap('Triangle');
let f = new shap(30,40)
f.DrawShap('a');
function company(name){
this.name = name;
}
var locationss = {
loc1:"Noida",
loc2:"sez"
}
company.prototype = locationss;
var icr = new company('icpl ');
console.log(icr.name + icr.loc2)
function parent (name){
this.run = 'i m running very fast'
this.name = name;
}
var p = new parent('John');
function child (name){
console.log('hi--' + p.name)
parent.call(this, name);
}
var Child = new child(p.name);
console.log(Child.name)
function Rectangle (height, width){
this.height = height;
this.width = width;
}
Rectangle.prototype.Area = function(){
this.area = this.height + this.width;
console.log(this.area)
return this.area;
}
var react1 = new Rectangle(4,6)
console.log(react1.Area())