JS challenge question help

Question

Hello community,

I have a question about the following code

(function() {
let a = b = 3;
})();
console.log(typeof a == "undefined");
console.log(typeof b == "number");

Why does first comparison evaluates to true? Doesnt a gets assigned value of b, which is three, because of the associativity? Instead, It looks like it is indeed undefined.

Answer 1

According to MDN
"a = b = 5; // same as writing a = (b = 5);"

It looks as if the let keyword only applies to variable a.
let a = b = 3 || let a = (b = 3)

It also appears that variable b is globally scoped, while variable a is block-scoped inside of the IFIIE, hence the reason both evaluations return true.

I ran the snippet on playground(web and node) and b is globally scoped
(CMIIW)

Answer 2

I thought it gets assigned value of 3 and so its typeof then changes to number. Thanks for your help though.

Answer 3

I didnt do this code myself, It was created by someone and is a legit question in challenges

Answer 4

You're welcome