Check browser version using Dart rather than JS? -

is there "angular/dart" way detect older unsupported browsers , prevent continue elegant message (there plenty of examples using javascript) rather continue , show weird layout code doesn't work?

even angulardart.org/demo site should imo stop ie8 (i know, enterprise customers still have old browsers installed - , set default - legacy apps) showing content doesn't work.

if dart code cannot executed test has done in js. i'm not aware of library makes test.

the test should follow what browsers support javascript compilation targets?.