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

>>5
You have to state the rule concerning which go into a particular key.
Clearly you haven't read your SICP today.

Have two lists: one octave using sharps and one using flats
Then, after using your rule [or prompting the user how the result should be expressed] perform the function on the appropriate octave.