Web audio Single class

Single.js

import fetchAudioBuffer from './helpers/fetch-audio-buffer';
import methodPatch from './helpers/method-patch';
import MobileAudioFix from './helpers/mobile-audio-fix';

// All of my MP3s were built to be a consistent volume on export,
// so I can safely set the same gain on all of them.
const singleGain = 0.6;

const assetPaths = {
  cubeUp: 'assets/audio/cube-up.mp3',
  // ...more paths...
};

export default class Single {
  static singleKeys = Object.keys(assetPaths);

  constructor() {
    this.context = new AudioContext();
    // Think of this as the "volume knob"
    this.gainNode = this.context.createGain();
    // `source` will be the active "sound"
    this.source = null;
    // Used to store all of my decoded sounds
    this.sounds = {};

    // Loop through all of my paths, fetch them,
    // and store their decoded AudioBuffer in the `sounds` object
    Single.singleKeys.forEach((key) => {
      fetchAudioBuffer(assetPaths[key], this.context).then((response) => {
        this.sounds[key] = response;
        return this.sounds[key];
      }).catch(() => {
        this.sounds[key] = null;
      });
    });

    this.mobileAudio = new MobileAudioFix(this.context);
    this.mobileAudio.init();
  }

  play(key) {
    if (!Single.singleKeys.includes(key)) {
      return Error(`The requested sound is not available: ${key}`);
    }

    return this._startSource(this.sounds[key]);
  }

  _startSource(sound) {
    // We need to create a `AudioBufferSourceNode` in order to attach
    // our individual decoded sound
    this.source = this.context.createBufferSource();
    this.source.buffer = sound;

    // Turn the volume knob up to a specific value at the current time
    this.gainNode.gain.setValueAtTime(
      singleGain,
      this.context.currentTime
    );

    this.source.connect(this.gainNode);
    this.gainNode.connect(this.context.destination);

    this.source.start = methodPatch.start(this.source);
    this.source.start();
  }
}