OLD-README.md

To copy an array

    var a = [1,2,3,4,5]
    var b = [...a]  //(three dots are spread operator)

To copy an obj

    var a = {Harsh}
    var b = {...a}

Falsy Values

    0 false undefined null NaN 

Truthy Values all except falsy

Loops

        foreach(
            works for looping on array
            works on each and every value "Har Ek"
        )

        forin(
            works for looping on objects
            key = key ki value
        )
    

Callback function = esa function jo tb chlta hai jb kaam complete ho jaaye

First class functions = iske according hum functions ko as a value use kr skte hai

Heap memory is used to store the data

Literals = Fixed Data Values = Numbers , Strings

Variables = Used to store data values

Identifiers are used to name variables and keywords, and functions they are also know as Unique Variables.

Keywords = let , var , const

Redeclaring

• let , const can not be re-decleared
• var can be redecleared

var x = 2;     // Allowed
var x = 3;     // Allowed
x = 4;         // Allowed

const x = 2;   // Allowed
x = 4;         // Not allowed
var x = 5;     // Not allowed
let x = 6;     // Not allowed
const x = 7;   // Not allowed

let x = 2;   // Allowed
x = 4;       // Not allowed
var x = 5;     // Not allowed
let x = 6;     // Not allowed
const x = 7;   // Not allowed

Operators in JS

Arithmetic Operators

• Addition

• Subtraction

• Multiplication ** Exponentiation / power x**2 is same as Math.pow(x,2) / Division % Modulus (Division Remainder) ++ Increment by 1 -- Decrement by 1

Assignment Operators

Operator	Usage	Expanded Form
=	x = y	x = y
+=	x += y	x = x + y
-=	x -= y	x = x - y
*=	x *= y	x = x * y
/=	x /= y	x = x / y
%=	x %= y	x = x % y
**=	x **= y	x = x ** y

Shift Assignment Operators (works on 32bit form of numbers) () <<= Left Shift Assignment Operator remove the left bit and add a 0 to the right side

= Right Shift Assignment Operator remove the right bit and add 0 to the left side

Data Types

let x = 16 + 4 + "Volvo";
// Output = 20Volvo

let x = "Volvo" + 16 + 4;
Volvo164
Empty value ("") = String

Functions

Executed only when it is invoked / called The code to be executed, by the function, is placed inside curly brackets: {} Hoisting works You can write code that can be used many time

function addTwoNumbers(a,b){
    let c = a + b;
    console.log(a + b)
}

addTwoNumber(5,7)  // Ouput => 12

Strings are written inside double or sinle quotes. Numbers are written without quotes.