eridal · July 18, 2018 18:09
diff --git a/scale-circles-generator.html b/scale-circles-generator.html
 <!DOCTYPE html>
 <title>Scale Circles Generator</title>
 <meta charset=utf-8>
 <style>
 canvas {
  border: 1px solid #eee;
 }
 </style>
 <body>
 <canvas width="500" height="500"></canvas>
 <script>
 // html
 let canvas = document.querySelector('canvas')
 let ctx = canvas.getContext('2d')

 // draw
 let cw = 500
 let ch = 500
 let ox = 0
 let oy = 0
 let deg = (i, scale) => {
  let d = 0
  for (let j = 0; j < i; j += 1) {
    d += scale[j]
  }
  return d
 }
 let cd = 6
 let rd = cw / 4
 let cs = 2
 let ng = (d) => 2 * Math.PI / 12 * (d + cd)
 let rx = (d) => rd * Math.sin(ng(d)) * -1
 let ry = (d) => rd * Math.cos(ng(d))

 let paint = {
  background() {
    ctx.fillStyle = 'white'
    ctx.fillRect(0, 0, cw, ch)
  },
  circle() {
    // circle
    ctx.beginPath()
    ctx.arc(ox, oy, rd, ng(0), ng(12))
    ctx.strokeStyle = '#aaa'
    ctx.stroke()
    // lines
    for (let d = 0; d < 12; d += 1) {
      ctx.beginPath()
      ctx.moveTo(rx(d) * 0.95,
                 ry(d) * 0.95)
      ctx.lineTo(rx(d) * 1.05,
                 ry(d) * 1.05)
      ctx.stroke()
    }
  },
  scale(scale) {
    // 1. build the scale
    let degs = [0]
    for (let i = 0, d = 0; i < scale.length - 1; i += 1) {
      d += scale[i]
      degs.push(d)
    }
    // 2. build the chords
    let funcs = []
    for (let i = 0; i < scale.length; i+= 1) {
      let d3 = degs[(i + 2) % degs.length]
             - degs[(i + 0) % degs.length]
      let d5 = degs[(i + 4) % degs.length]
             - degs[(i + 0) % degs.length]
      if (d3 < 0) d3 += 12
      if (d5 < 0) d5 += 12
      let c = `${d3}/${d5}`
      funcs.push(chords[c])
    }
    // 2. draw the path
    ctx.beginPath()
    for (let i = 0; i < scale.length; i += 1) {
      let d = degs[(i * cs) % 7]
      if (d == 0) {
        ctx.moveTo(rx(d), ry(d))
      } else {
        ctx.lineTo(rx(d), ry(d))
      }
    }
    ctx.closePath()
    ctx.strokeStyle = '#333'
    ctx.stroke()

    // notes names
    ctx.font = '12px sans-serif'
    for (let i = 0, d = 0; i < notes.length; i += 1) {
      d += scales.major[i]
    }

    // 3. draw the notes
    ctx.fillStyle = '#333'
    for (let i = 0; i < scale.length; i += 1) {
      let d = deg(i, scale)
      let m = deg(i, scales.major)
      let a = d == m ? '' : d < m ? '♭' : '♯'
      let f = funcs[i]
      ctx.fillText(notes[i] + a + f, rx(d) * 1.2, ry(d) * 1.2)
    }
    // 4. title
    ctx.fillText(scale.name, -1 * scale.name.length, 0)
  }
 }

 // scales
 let notes = [ 'C', 'D', 'E', 'F', 'G', 'A', 'B' ]
 let chords = {
  '3/6': '°',   // dim
  '3/7': 'm',   // min
  '4/7': '',    // maj
  '4/8': '+',   // aug
 }
 let major = [ 2, 2, 1, 2, 2, 2, 1 ]
 let scales = {
  major: 0,
  minor: 5,
  ionian: 0,
  dorian: 1,
  phrygian: 2,
  lydian: 3,
  mixolydian: 4,
  aeolian: 5,
  locrian: 6,
 }
 let mode = (m) => {
  let scale = []
  for (let i = 0; i < major.length; i += 1) {
    let d = (i + m) % major.length
    scale.push(major[d])
  }
  return scale
 }
 Object
  .keys(scales)
  .forEach(name => {
    scales[name] = mode(scales[name])
    scales[name].name = name
  })

 function draw(scale) {
  canvas.width = canvas.width
  paint.background()
  ctx.translate(cw / 2, ch / 2)
  paint.circle()
  paint.scale(scale)
 }

 let names = Object.keys(scales)
 let r = Math.round(Math.random() * names.length) % names.length
 let name = names[r]
 draw(scales[name])
 //draw(scales.major)
 </script>
 </body>
	<!DOCTYPE html>
	<title>Scale Circles Generator</title>
	<meta charset=utf-8>
	<style>
	canvas {
	border: 1px solid #eee;
	}
	</style>
	<body>
	<canvas width="500" height="500"></canvas>
	<script>
	// html
	let canvas = document.querySelector('canvas')
	let ctx = canvas.getContext('2d')

	// draw
	let cw = 500
	let ch = 500
	let ox = 0
	let oy = 0
	let deg = (i, scale) => {
	let d = 0
	for (let j = 0; j < i; j += 1) {
	d += scale[j]
	}
	return d
	}
	let cd = 6
	let rd = cw / 4
	let cs = 2
	let ng = (d) => 2 * Math.PI / 12 * (d + cd)
	let rx = (d) => rd * Math.sin(ng(d)) * -1
	let ry = (d) => rd * Math.cos(ng(d))

	let paint = {
	background() {
	ctx.fillStyle = 'white'
	ctx.fillRect(0, 0, cw, ch)
	},
	circle() {
	// circle
	ctx.beginPath()
	ctx.arc(ox, oy, rd, ng(0), ng(12))
	ctx.strokeStyle = '#aaa'
	ctx.stroke()
	// lines
	for (let d = 0; d < 12; d += 1) {
	ctx.beginPath()
	ctx.moveTo(rx(d) * 0.95,
	ry(d) * 0.95)
	ctx.lineTo(rx(d) * 1.05,
	ry(d) * 1.05)
	ctx.stroke()
	}
	},
	scale(scale) {
	// 1. build the scale
	let degs = [0]
	for (let i = 0, d = 0; i < scale.length - 1; i += 1) {
	d += scale[i]
	degs.push(d)
	}
	// 2. build the chords
	let funcs = []
	for (let i = 0; i < scale.length; i+= 1) {
	let d3 = degs[(i + 2) % degs.length]
	- degs[(i + 0) % degs.length]
	let d5 = degs[(i + 4) % degs.length]
	- degs[(i + 0) % degs.length]
	if (d3 < 0) d3 += 12
	if (d5 < 0) d5 += 12
	let c = `${d3}/${d5}`
	funcs.push(chords[c])
	}
	// 2. draw the path
	ctx.beginPath()
	for (let i = 0; i < scale.length; i += 1) {
	let d = degs[(i * cs) % 7]
	if (d == 0) {
	ctx.moveTo(rx(d), ry(d))
	} else {
	ctx.lineTo(rx(d), ry(d))
	}
	}
	ctx.closePath()
	ctx.strokeStyle = '#333'
	ctx.stroke()

	// notes names
	ctx.font = '12px sans-serif'
	for (let i = 0, d = 0; i < notes.length; i += 1) {
	d += scales.major[i]
	}

	// 3. draw the notes
	ctx.fillStyle = '#333'
	for (let i = 0; i < scale.length; i += 1) {
	let d = deg(i, scale)
	let m = deg(i, scales.major)
	let a = d == m ? '' : d < m ? '♭' : '♯'
	let f = funcs[i]
	ctx.fillText(notes[i] + a + f, rx(d) * 1.2, ry(d) * 1.2)
	}
	// 4. title
	ctx.fillText(scale.name, -1 * scale.name.length, 0)
	}
	}

	// scales
	let notes = [ 'C', 'D', 'E', 'F', 'G', 'A', 'B' ]
	let chords = {
	'3/6': '°', // dim
	'3/7': 'm', // min
	'4/7': '', // maj
	'4/8': '+', // aug
	}
	let major = [ 2, 2, 1, 2, 2, 2, 1 ]
	let scales = {
	major: 0,
	minor: 5,
	ionian: 0,
	dorian: 1,
	phrygian: 2,
	lydian: 3,
	mixolydian: 4,
	aeolian: 5,
	locrian: 6,
	}
	let mode = (m) => {
	let scale = []
	for (let i = 0; i < major.length; i += 1) {
	let d = (i + m) % major.length
	scale.push(major[d])
	}
	return scale
	}
	Object
	.keys(scales)
	.forEach(name => {
	scales[name] = mode(scales[name])
	scales[name].name = name
	})

	function draw(scale) {
	canvas.width = canvas.width
	paint.background()
	ctx.translate(cw / 2, ch / 2)
	paint.circle()
	paint.scale(scale)
	}

	let names = Object.keys(scales)
	let r = Math.round(Math.random() * names.length) % names.length
	let name = names[r]
	draw(scales[name])
	//draw(scales.major)
	</script>
	</body>