const a = 10;
function f() {
var/let a = 9
console.log(a)
}
f();//9

It seems there's a small error in your code. The correct code snippet would be:

Copy code
const a = 10;

function f() {
    let a = 9;
    console.log(a);
}

f(); // Output: 9
In this corrected code:

The constant variable a is declared outside the function f with a value of 10.
Inside the function f, a new variable a is declared using the let keyword, and it has a value of 9.
The console.log(a) statement inside the function will print the value of the local variable a, which is 9.
When you call the function f() at the end, it prints 9 to the console.
If you intended to use var instead of let, the corrected code would be:

Copy code
const a = 10;

function f() {
    var a = 9;
    console.log(a);
}

f(); // Output: 9

Both versions are valid, but using let is generally recommended for declaring block-scoped variables in modern JavaScript.