I want to construct a web page with an html form with some input
fields. Some require input in Korean and others in English. User would
usually hit right "alt" key to switch between two languages.

Is there a way (probably using Javascript) to assign default language
setting to each input field, so the input language would be
automatically determined for each input field?

If the answer is "yes" and you can show me how to, I will double the reward.