"Uncaught ReferenceError: a is not defined" instead of "ReferenceError: Cannot access 'a' before initialization"

In this simple code, since the variable b is a let variable and i am trying to log() its value, I was expecting a reference error that said: cannot access ‘a’ before initialization,

but instead i am getting the error:
Uncaught ReferenceError: a is not defined

console.log(a);
let a=10;
var b=19;

a screenshot of the code and the error–>

i ran the same code in online js editors and they give the expected error, i am confused now :
the same code on an online editor with different error

>Solution :

According to error docs it happens within any block statement

Since you don’t have block statement, JS fires another error.

I suppose that in online editor, the code is executed by another code, so there could be block statement outside the "file".