This code section is loading within the actual worker (and assumes that dojo.js was loaded into the worker via importScripts).  The importScripts function will map relative urls from the root of parent page rather than the executing script.  Hence: ./_base/configWorker.js will not load the expected path, which is a disappointing.  We need first to calculate the path that dojo itself loaded from then map the relative configWorker.js path onto that.

I'm not sure there is a way around this particular annoyance? I have spent a lot of time researching it and trying different approach but always hit a blank.

I will add some comments so that the logic here is a bit clearer, otherwise it is a bit of a black box.