Is it possible to clear and populate a select list client side.

I have a ASP page which on the server side provides two select lists which 
are of parent and child records.

I was thinking of saving the records in cookies as arrays so that I could 
pick them up client side via a bit of JavaScript.
The first select list dictates the options of the second and to stop a 
round trip to the server I thought yes a little Java and Bobs my aunties 
live in lover.

Firstly is it possible to clear and populate the Select Lists client side 
and does anyone have a better method for transfering server side varibles 
to a working client side method?

Thanks
Stuart