modes.js

#!/usr/bin/env node

var modes = ['Ionian', 'Dorian', 'Phrygian', 'Lydian', 'Mixolydian', 'Aeolian', 'Locrian'];
var steps = [2, 2, 1, 2, 2, 2, 1];
var notes = ['C', 'C#/Db', 'D', 'D#/Eb', 'E', 'F', 'F#/Gb', 'G', 'G#/Ab', 'A', 'A#/Bb', 'B'];
var noteRoots = ['C', 'D', 'E', 'F', 'G', 'A', 'B'];

function getNotes(scale, mode) {
	if(mode === 'Major') {
		mode = 'Ionian';
	} else if(mode === 'Minor') {
		mode = 'Aeolian';
	}
	var modeOffset = modes.indexOf(mode);
	var currIndex = getValue(scale);
	var currRootIndex = noteRoots.indexOf(scale.slice(0, 1));
	var outList = [scale];
	for(var i = 0; i < steps.length - 1; ++i) {
		var toAdd = steps[(i + modeOffset) % steps.length];
		currIndex = (parseInt(currIndex) + toAdd) % notes.length;
		outList.push(getNextNote(currRootIndex, currIndex));
		currRootIndex++;
		currRootIndex %= noteRoots.length;
	}
	return outList.map(function(note){
		return note.replace(/b/g, '♭').replace(/#/g, '♯');
	});
}

function getValue(note) {
	var value = 0;
	for(var i in note) {
		if(note[i] == '#') {
			value++;
		} else if(note[i] == 'b') {
			value--;
		}
	}
	return (value + notes.indexOf(note.slice(0,1))) % notes.length;
}

function getNextNote(rootIndex, value) {
	var outNote = noteRoots[(rootIndex + 1) % noteRoots.length];
	var genValue = getValue(outNote);
	var possibleDiffs = [
		(value - genValue),
		(12 + value - genValue),
		(-12 + value - genValue)
	];
	var minIndex = 0;
	var diff = possibleDiffs[minIndex];
	possibleDiffs.forEach(function(num, idx){
		if(Math.abs(num) < Math.abs(possibleDiffs[minIndex])) {
			minIndex = idx;
		}
	});
	if(diff > 0) {
		while(diff--) {
			outNote += '#';
		}
	} else if(diff < 0) {
		while(diff++) {
			outNote += 'b';
		}
	}
	return outNote;
}

modes.forEach(function(mode) {
	console.log(process.argv[2] + ' ' + mode, getNotes(process.argv[2], mode));
});