Hello Sir/Madam,

I have one doubt regarding this question
(function fn() {
{
let a = 10;
{
var a = 20;
console.log(a);
}
} })();

why it is giving syntax Error ?
I know this is illegal shadowing concept but when I put braces before let a =10, then that a variable has block scoped and var a is function scoped, here after adding curly braces before let a , I have create new scope and after fn(){ // here var a is hoist}, then if both are in different scope , why it is showing error.

Please help in explaining this concept.

Thank You

On Friday, 6 August 2021 at 11:53:53 UTC+2, gaura...@gmail.com wrote:
> Hello Sir/Madam,
>
> I have one doubt regarding this question
> (function fn() {
> {
> let a = 10;
> {
> var a = 20;
> console.log(a);
> }
> }
> })();
>
> why it is giving syntax Error ?
> I know this is illegal shadowing concept but when I put braces before let a =10, then that a variable has block scoped and var a is function scoped, here after adding curly braces before let a , I have create new scope and after fn(){ // here var a is hoist}, then if both are in different scope , why it is showing error.

They are not in a different scope: "let a" is in the *top* block scope of the function, which is the entire function, but so is "var a", as that's how var scoping works.

> Please help in explaining this concept.

Have a read through this and related:
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let>
The very last example is your case.

HTH,

Julio