It starts out with a label that does nothing because there is no loop (presumably the author thinks they are saying "this is JavaScript" (they aren't)).
Then it calls a function with two arguments, a string (made up of concatenating some other strings and the return value of another function call) and a boolean.
You haven't shared those two functions with us (and they aren't JS built-ins or browser build-ins) so we have no idea what they might do.