Use audio analyzer to create an equalizer on your browser

equalizer.js

/**
 * Originally created by @jake_albaugh (Twitter)
 * UTF8 characters starting from "\u2581"
 */
const l = ["▁", "▂", "▃", "▄", "▅", "▆", "▇", "█"];
const x = new AudioContext();
const a = x.createAnalyser();
a.fftSize = 32;
const d = new Uint8Array(16);

navigator.mediaDevices.getUserMedia({ audio: true }).then(s => {
  x.createMediaStreamSource(s).connect(a);
  z();
});

function z() {
  setTimeout(z, 40);
  a.getByteFrequencyData(d);
  const data = Array.from(d);
  const s = data.map(v => l[Math.floor((v / 255) * 8)]);
  window.location.hash = document.title = s.join("");
  document.title = s.join("");
  const outStr = s.join("");
  window.history.replaceState("", outStr, outStr);
}