Best way to create text file in a user defined local directory?

[Cohoman]

I'm trying to create and write to a text file in a user defined local folder from within a web worker js file. I tried using requestFileSystemSync(), .root.getFile(), .createWriter(), etc. but I'm not sure where this file is saved (can it be written to an defined local folder, or is it "sandboxed" to a special folder location?).

Can anyone offer advice on the best way for me to create text files from a web worker to an arbitary local folder location?

Thanks.