musical transposition in javascript

I'm trying to make a transposer in JavaScript..
Give it a key and a scale/mode and it will generate it for you
For instance
C Lydian (WWWHWWH) is C D E F# G A B
C Aeolian (WHWWHWW) is C D Eb F G Ab Bb
I cannot for the life of me figure out how to accomplish this.
Thoughts?
>inb4 SICP

>>21
Alright, thanks teech.