const, let and var in JavaScript

console.log("JavaScript tutorial: var, let and const");

var a = 45;     //It is recommended to use "let" and "const" in place of "var"

var b = "Harry";

// b = 4

let b2 = "Harry2";

// let c = null    //"let" can be updated but not re-declared

// let d = undefined

// const author = "Harry is author"

// let author = 5  //Throws an error because constant cannot be changed

// author = 10     //Throws an error because constant cannot be changed

//"const" can neither be updated nor be re-declared

//"const" must be initialized during declaration unlike let and var

// const bird; //Throws an error because "const" must be initialized during declaration

{

    var b = "this"

    console.log(b)

}

console.log(b)

{

    let b2 = "this2" //"let" and "const" are block scoped

    console.log(b2)

}

console.log(b2)

OUTPUT :

JavaScript tutorial: var, let and const this this this2 Harry2