How do I transpose music chords using JavaScript?

Question

I was wondering how would one create a javascript function for transposing music chords.

Since I don\'t expect everyone to be a musician here, I\'ll try to explain how i

Answer 1

Just to expand on nnnnnn's answer. We can take his code and add a little bit more code to actually make it work with flats.

transposeChord("F#sus7/A#", 1)
> "Gsus7/B"

transposeChord("Bb", 1)
> "B"

... works like a charm

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

Chord:         
transposed by  
=             
              Calculate