notes.txt

Variables
Operators
Datatypes
Alert,prompt,confirm

Variables:- It is name given to memory location.
=>var 
=>let
=>const

var :-
=> It is keyword to declare Variables.
=> It can be redeclared and reassigned.
Ex:-
var a = 10;
a=20; //reassign
var a = 30; //redeclare
console.log(a);

let:-
=> It is keyword to declare Variables.
=> It can be only reassigned.
let a =10;
a=30; //reassign
console.log(a);

const:-
=> It is keyword to declare Variables.
=> It cannot be redeclared and reassigned.
const c = 10;
console.log(c);

Operators:-
=>Airthmetic Operators: +,-,*,/,%
=>Assignment Operator: =
=>Conditional Operators: <,>,<=,>=,!=,!==,==,===
=>Logical Operators: & ,||

Window methods/events:-
Alert:- 
alert("Click Ok to enter into the website")

Prompt:-
let result = prompt("Enter your Name")
console.log(result)

Confirm:-
let result1= confirm("Are you sure to enter the webiste")
console.log(result1);

Datatypes:- 
String,Number,Boolean,Array,Object,Bignint,Symbol,Null,Undefined,Functions

Undefined:- 
=> If a variable is declared but the value is not assigned,
then the value of that variable is undefined.
=> Then the datatype is also undefined.
Example:-
let a;
console.log(a);

Null:- 
=> Null is a special value that represents empty or unknown values
=> The type of null will be an object.
=> It is a known bug in Javascript.
=> Javascript defines that null is equal to undefined.
Example:-
let num = null;
console.log(num);
console.log(typeof(num));

Object:- 
=>Object is a collection of properties
=>Object are structured with key value pair
=>Objects do not have index
syntax:-
var/let/const objectname ={
    keyname:value
} 
Example:-
let person = {
    firstname:"John",
    lastname:"Doe",
    age:35,
    gender:"Male",
    phonenumber:9876543210,
    skills:["Javascript","HTML","CSS","Reactjs"]
}
console.log(person);