little hint : . . .

okkOokOo('Ok, Ook, Ooo!')  // -> 'H'

. . . let's say we remove commas & spaces, . . . now what if chars were numbers ( what kind of number may be a "O" or "o" , or a "k" (compared to "o" of course)) ) ? . . . and now what if compared to H ? . . .

Hope it helps.
; ) )