ChordGenerator.js

function random(a, b) { 
    if(Array.isArray(a)){
        return a[random(a.length)];
    } 
    if (typeof a === "object") {
        var key = random(Object.keys(a)); 
        return b === "key" ? key : b === "both" ? {key:key,value:a[key]} : a[key];
    }
    if (typeof a === "string" && !!a) {
        return (a.toLowerCase() === "bool") ? (Math.floor(Math.random()*2) == 1) : random(a.split(''));
    }
    if (typeof a === "number"){
        if(typeof b === "number"){
            return random(b-a)+a;
        } 
        return Math.floor(Math.random()*a);
    }
    return false;
};

function getMajorScaleChordLabels(key, chordNumbers) {
    var notes = ['C','C#','D','D#','E','F','F#','G','G#','A','A#','B'];
    
    var chordMap = {
        1: { position: 0,  shape: 'Maj' },
        2: { position: 2,  shape: 'm'   },
        3: { position: 4,  shape: 'm'   },
        4: { position: 5,  shape: 'Maj' },
        5: { position: 7,  shape: 'Maj' },
        6: { position: 9,  shape: 'm'   },
        7: { position: 11, shape: 'Dim' }
    };
    var chords = [];
    for (var i = 0; i < chordNumbers.length; i++) {
        var chord = chordMap[chordNumbers[i]];
        var typeExtension = chord.shape == 'Maj' ? '' : chord.shape;
        chords.push(notes[((key + chord.position) % notes.length)] + typeExtension); 
    }
    return chords;
}

function randomProgression() {
    var chords = [1];
    for (var i = 0; i < 3; i++) {
        chords.push(random(1,6));
    }
    return chords;
}

// getMajorScaleChordLabels(random(0,11),randomProgression())