光の強さに応じて音階が変わるアプリ

gistfile1.js

const PITCH = [
  220 * Math.pow( 1.06, 3 ), // ド
  220 * Math.pow( 1.06, 4 ), // ド#
  220 * Math.pow( 1.06, 5 ), // レ
  220 * Math.pow( 1.06, 6 ), // レ#
  220 * Math.pow( 1.06, 7 ), // ミ
  220 * Math.pow( 1.06, 8 ), // ファ
  220 * Math.pow( 1.06, 9 ), // ファ#
  220 * Math.pow( 1.06,10 ), // ソ
  220 * Math.pow( 1.06,11 ), // ソ#
  440, // ラ
  440 * Math.pow( 1.06, 1 ), // ラ#
  440 * Math.pow( 1.06, 2 ) // シ
];
const DEFAULT_PITCH = PITCH[0];

var indicator;
var audioContext;
var oscillator;

var displayBrightness = function(element, value){
  element.textContent = value;
};

var changePitch = function(value){
  oscillator.frequency.value = value;
};

var lux2Pitch = function(lux){
  var index = Math.floor(Math.max(100, Math.min(1100, lux)) / 100);
  return PITCH[index];
};

var handleDeviceLightEvent = function(event){
  var lux = event.value;
  if(indicator != null){
    displayBrightness(indicator, lux);
  }
  changePitch(lux2Pitch(lux));
};

var initApp = function(){
  indicator = document.querySelector("h1");

  audioContext = new AudioContext();
  oscillator = audioContext.createOscillator();
  oscillator.type = "sawtooth";
  oscillator.frequency.value = DEFAULT_PITCH;
  oscillator.connect(audioContext.destination);
  oscillator.start();
};
 
window.addEventListener("load", initApp);
window.addEventListener("devicelight", handleDeviceLightEvent);