On Form load js

Hello guys,

I have one problem when i am writing the javasript on form load.

Requirement:

1)In option set multiple values are there.If the form is loading then its show only two values in option set remaining values is not required to show.Its my requirement one.

I have one another problem when i am writing js on change.

2)If i select value in option set (CCtype) then its show 3 values 1 is americanexpress (15 digit required) 2 is mastercard(16 digit required) 3 is visa(13 or 16 digit required).Its my requirement second.

Plz help me out.