Scope level and mini hoisting

Global and local scope

let a = 10

const b = 20

Var c = 30

console.log(a)

console.log(b)

console.log(c)

• If var is working then why let and const?

\=> Because var doesn’t work in block scope.

{ } => scope when it comes with a conditional statement or loop or function

If(true){

    let a =10;

    const b = 20;

    Var c = 30;

}

console.log(a) // this will give error

console.log(b) // this will also give error

console.log(c); // this will print 30 and 
//this is the problem and thus starts the concept of 
//scope and we should avoid using "var"

let a = 300; //global scope

If(true){

    let a = 30; // block scope

    console.log(a); // this will print 30

}

console.log(a) // this will print 300

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function one (){

    const username = "harsh"

function two (){

    const web = "yt"

console.log(username) //this will give no error as child function can access variables of parent function.


}

    console. log(website) //error as website not defined

two()

}

one()

// Child function can access variables of parent function but parent function can't access variables of child function.

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Concept of hoisting in brief:-

addOne(num) // if I call function here it will still work because of the way it has been initialized .

function addOne(num){

return num + 1;

}

addTwo() // this will give error as not initialized because of the way function has been initialized.

const addTwo = function(num){

return num + 2;

}

addTwo () // it must be called after initializing.