simple transpose

transpose.js

//from http://stackoverflow.com/a/7936999

function transposeChord(chord, amount) {
  var scale = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"];
  return chord.replace(/[CDEFGAB]#?/g,
                       function(match) {
                         var i = (scale.indexOf(match) + amount) % scale.length;
                         return scale[ i < 0 ? i + scale.length : i ];
                       });
}

alert(transposeChord("Dm7/G", 2)); // gives "Em7/A"
alert(transposeChord("Fmaj9#11", -23)); // gives "F#maj9#11"