Automatic introduce the last part of a time field

How can I automatically introduce, in a time field, the last two digits from time. What i mean is I write 16:开发者_开发百科 in the field and it automatically puts the last 00. Something in javascript? thank you

1. listen to the keyup or keypress event,
2. test if it's a :,
3. test if the two characters before the : are valid
4. add 00