show major/minor scales

show_major_minor_scales.js

// https://wandbox.org/permlink/oFiLhUB4zQ73nxTx

const kCMajorScale = ["C", "D", "E", "F", "G", "A", "B"];
const kAMinorScale = ["A", "B", "C", "D", "E", "F", "G"];

const ScaleShiftDirection = {
    kDominant: 0,
    kSubdominant: 1,
}

function shiftScale(step, direction, isMajor) {
    var tmp = (isMajor ? kCMajorScale : kAMinorScale).slice();

    console.assert(step <= 7);
    for(var i = 0; i < step; ++i) {
        if(direction == ScaleShiftDirection.kDominant) {
            tmp = tmp.slice(4, 7).concat(tmp.slice(0, 4));
            tmp[(isMajor ? 6 : 1)] += "#";
        } else {
            tmp = tmp.slice(3, 7).concat(tmp.slice(0, 3));
            tmp[(isMajor ? 3 : 5)] += "b";
        }
    }
    
    return tmp;
}

function showScales(isMajor) {
    console.log(shiftScale(0, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(1, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(2, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(3, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(4, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(5, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(7, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(6, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(6, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(7, ScaleShiftDirection.kDominant, isMajor));
    console.log(shiftScale(5, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(4, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(3, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(2, ScaleShiftDirection.kSubdominant, isMajor));
    console.log(shiftScale(1, ScaleShiftDirection.kSubdominant, isMajor));
}

showScales(true);
console.log("");
showScales(false);