To make the solution by you two a bit more elegant, a new (as explained here) block of a Reporter type is needed.
not really important
See it in project Media_Map_with_JS_block {the link will open it in editMode & noRun} within my "Output" sprite there you can see the custom block I made; it works, again, just fine, however it reports an error and I'd appreciate explanation for it. (I have tested the custom block on its own and it works just fine, so why it reports an error?)
EDIT: maybe this thread/topic should be split