I think they meant to say block scoped variables. In js everything is function scoped or global (until you get to ES 6 "let" and "const" variables). As far as

I think they meant to say block scoped variables. In js everything is function scoped or global (until you get to ES 6 "let" and "const" variables). As far as web workers, they are very restricted/isolated compared to regular shared memory threads In other languages.