Note.txt

Contents:
Introduction to Array
Array and Object JSON iteration
Array & Object Destructuring [] {key}
object.this Method
Create New Objects Using New Method

Objects:- 
=>Js objects are data structures used to store and organize data.
=>Objects are variables too.
=>objects always declared in key-value pairs
=>Object is called real time entity (touch and feel)
=>But object contains many values & can be with different datatypes
var/let/const objectname =
{
    key: value
}
Example:-
=> A car has prop like weight and color & methods like start and stop
=> All car has same method but prop differ from car to car

=> There are 2 ways to declare objects.
1. to declare objects using curly brackets {}
const person ={
    name: "Rajini",
    age: 45,
    occupation: "actor"
}
=> to print the output in object we have 2 methods
**dot notation
console.log(person.name); // Rajini
console.log(person.age); //45
console.log(person.occupation); //actor
**square brackets
console.log(person["name"]);// Rajini
console.log(person["age"]);// 45
console.log(person["occupation"]);// actor
2. to declare objects using new methods (Object constructor using the new keyword)
const person = new Object();
person.name = "rajini";
person.age = 45;
person.occupation = "actor";

==>Modifying the Object
const person = {
    name: "rajini",
    age: 45
}
=> there are two methods to modify object
1.dot notation
person.name= "kamal"
console.log(person); 
//{name:"kamal",age:45}
2.square brackets
person["age"]=60;
console.log(person); 
//{name:"kamal",age:60}

==>Adding a new property
const person = {
    name:"kamal",
    age:60
}
 person.occupation= "actor"
 console.log(person);
 //{name:"kamal",age:60,occupation:"actor"}

 ==>Removing Obj property
 const person = {
    name:"kamal",
    age:60,
    city: "chennai"
}
delete person.city // it will delete the city prop in obj
console.log(person);
 //{name:"kamal",age:60}
 **------------------------------------------------------------**
==> Array and Object JSON iteration
JSON:- 
=>(Javascript Object Notation) is a lightweight data interchange format.
=>It uses key value pairs
=>similar to object
=>the synatx consists of 2 types {} is for object json , [] is for array json
====>JSON Object
const person={
    name: "kamal",
    age:60
}
===>JSON Array
const fruits = ["apple","banana","orange"]

==>Parse JSON : to convert a json string into a javascript object.
synatx: JSON.parse()
example:
const a = '{"name":"kamal","age":60}'; 
console.log(a);
var b = JSON.parse(a);
console.log(b);
==>JSON.stringify : to convert a javascript object into a json string.
const c = {
    name: "kamal",
    age: 60
}
console.log(c)
const d = JSON.stringify(c);
console.log(d)

==>Nested JSON object
var person = {
    "name":"kamal",
    "age" :60,
    "occupation":"actor",
    "address": {
        "city" : "chennai",
        "pincode" : 60001
    }
}
console.log(person)
console.log(person.address.city)

==>Nested JSON array
var person = [
    {
        "name":"kamal",
        "age":60
    },
    {
        "name":"rajini",
        "age":55
    }
]
console.log(person)
console.log(person[1].age)//55
**--------------------------------------**
Array & Object Destructuring
==>Array Destructuring
const arr = [1,2,3];
const[x,z,wwww,d=4]= arr;
console.log(x);
console.log(z);
console.log(wwww);
console.log(d);
console.log(arr);
 ==> Object Destructuring
 const obj = {
    name: "kamal",
    age:60,
    address:{
        city: "chennai",
        pin: 60001
    }
 }
//const{key}=objectname
const {name,age}= obj;
console.log(name);
console.log(age);
without Destructuring
//console.log(obj.address.city)
****-----------------------------------------***
Use Strict in Js
without strict mode
fullname = "kamal"
console.log(fullname)
with strict mode
'use strict';
fullname = "kamal"
console.log(fullname)
*************------------------------------**********
object.this Method
=>this keyword refers to an object
=> Which object depends on how this is being invoked(used or called)
1. Using "this" keyword alone, refers to global object
2. In regular function , refers to global object
3. In a function in strict mode , "this" is undefined.
4. In a method, "this" refers to the owner object.
Example:-
1. Using "this" keyword alone, refers to global object
console.log(this);
2.In regular function , refers to global object
const a = function(){
    console.log("hello world");
    console.log(this)
}
a();
3. In a function in strict mode , "this" is undefined.
'use strict';
const a = function(){
    console.log("strict mode");
    console.log(this)
}
a();
4. In a method, "this" refers to the owner object.
const person = {
    names : "kamal",
    age: 60,
    occupation: "actor"
    detail: function(){
        console.log(`I love ❤ ${this.names}`)
    }
}
console.log(person.detail());
***------------------------------------------------------****
Javascript Object methods
1.Object.assign();
2.Object.create();
3.Object.entries();
4.Object.freeze();
5.Object.keys();
6.Object.values();
7.Object.seal();
*************---------------------------------------------**********
title caps steps:
tolowercase
split
for loop
charAt(0)
touppercase
slice
join

palindrome steps
slice
tostring
split
reverse
join
for()
push