And in the newest installment, https://github.com/google/closure-library/issues/883 https://github.com/google/closure-library/issues/883 is UA-sniffing that is

And in the newest installment, https://github.com/google/closure-library/issues/883 https://github.com/google/closure-library/issues/883 is UA-sniffing that is now preventing Firefox from aligning with all other browsers on whether arrow keys fire keypress events, which causes _other_ Google things, which assume they don't, to break. Also Closure assumes that only things with "WebKit" in their UA might be running on a mobile device and that all browsers fall into the WebKit/IE/Edge/Gecko buckets (and will fail badly if a browser does not). And this is just one library.