origin

The global origin read-only property returns the origin of the global scope, serialized as a string.

A USVString.

Executed from inside a worker script, the following snippet will log the worker's global scope's origin to the console each time it receives a message

onmessage = function() {
  console.log(self.origin);
};

If the origin is not a scheme/host/port tuple (say you are trying to run it locally, i.e. via file:// URL), origin will return the string "null".