letconstvar.js

//Let,const & var

// 1. let : Variable cannot be re-declared but can be updated. A block scope variable.
// 2. const : Variable cannoot be re-declared or updated. A block scope variable.
// 3. var : Variable can be re-declared & updated. A global scope variable.


// let name = "Tony stark";
// let age = 24;
// let totalPrice = 99.99;
// console.log(name);
// console.log(age);
// console.log(totalPrice)


// 1. Example with let
// let age = 45;
// let age = 47;
// console.log(age); it will through an error like : Cannot redeclare block-scoped variable 'age'

// 1.1 Example with let
// let age = 45;
// age = 47;
// console.log(age); // Now it will through an updation of age to 45 to 47 
//it will show : 47


// 2. Example with const :
// const age = 17;
// console.log(age); it will print 17 without showing an error
// use case of const : in math equation.

// const age = 17;
// age = 18;
// console.log(age);
// it will show an error because of re-updation : letconstvar.js:33 Uncaught TypeError: Assignment to constant variable


// 3. Example with var
// var age = 24;
// var age = 29;
// var age = 89;
// console.log(age);
// Output will be 89 becuse of its re-declaretions & quietly updation.



//Some of extra learnable things :

// let a; //just declaring a variable without putting any data or only showcasing a variable name declare with name 'a'
// console.log(a);
//Output will be :  undefined. 
//because of no any kind of data declaration.

//Same of extra learnable things for : const
// const a;
// console.log(a);
//Output will always shows an error : Uncaught SyntaxError: Missing initializer in const declaration 
//Because of not declaring any data , Hence const should alwaye be declared!





//block in programming: 
// {
//     let a = 5;
//     console.log(a);
//
// }

//but in block
// {
//     let a = 5;
//     let a = 12;
//     console.log(a);
// }
//In this case it shows an error : Cannot redeclare block-scoped variable 'a'. 
//Because of block 

//but you can define or re-declare variable via declaring blocks seperately :
// {
//     let a = 5;
//     console.log(a);

// }

// {
//     let a = 12;
//     console.log(a);
// }

//Now output shows seperately two both variable with same declaration via no any throwing an