JSFiddle - React, Tailwind, and code Playground

by Lazaro Contreras

HTML

<canvas id="oscilloscope"></canvas>
<audio autoplay controls></audio>

JavaScript

var audioCtx = new(window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();

var audio = document.querySelector('audio');
audio.crossOrigin = "anonymous";
audio.src = "https://a.tumblr.com/tumblr_nyag1wXeQs1sdvzwso1.mp3";
audioSource = audioCtx.createMediaElementSource(audio);
audioSource.connect(analyser);
analyser.connect(audioCtx.destination);

// ...

analyser.fftSize = 2048;
var bufferLength = analyser.frequencyBinCount;
var dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);

// Get a canvas defined with ID "oscilloscope"
var canvas = document.getElementById("oscilloscope");
var canvasCtx = canvas.getContext("2d");

// draw an oscilloscope of the current audio source

var d = new Date();
var colorcount = 0;

function draw() {
	colorcount += d.getSeconds() / 10;
  requestAnimationFrame(draw);

  analyser.getByteTimeDomainData(dataArray);

  canvasCtx.fillStyle = "rgb(3, 3, 3)";
  canvasCtx.fillRect(0, 0, canvas.width, canvas.height);

  canvasCtx.lineWidth = 2;
  canvasCtx.strokeStyle = "hsl(" + colorcount + ",100%, 50%)";
  //canvasCtx.strokeStyle = "rgb(0, 0, 0)";

  canvasCtx.beginPath();

  var sliceWidth = canvas.width * 1.0 / bufferLength;
  var x = 0;

  for (var i = 0; i < bufferLength; i++) {

    var v = dataArray[i] / 128.0;
    var y = v * canvas.height / 2;

    if (i === 0) {
      canvasCtx.moveTo(x, y);
    } else {
      canvasCtx.lineTo(x, y);
    }

    x += sliceWidth;
  }

  canvasCtx.lineTo(canvas.width, canvas.height / 2);
  canvasCtx.stroke();
}

draw();