Dynamic creation and cleanup

Sometimes You only need a peak meter for some of the time that the page is loaded. For those cases, a peak meter instance can by dynamically created and cleaned up.

Working Example

The web audio API context is loading. Loading

HTML code

<p>
  The web audio API context is <span id="ctx-status">loading</span>.
  <button id="ctx-button">Loading</button>
</p>

<audio id="the-audio" preload="metadata" crossorigin="anonymous" controls="controls">
  <source src="https://assets.rpy.xyz/testmedia/semper_fidelis.mp3" type="audio/mpeg" />
</audio>
<div>
  <button id="meter-toggle">Create meter</button>
</div>
<div id="peak-meter" style="height: 80px"></div>

Javascript code

const audioCtx = new AudioContext();
const audioElement = document.getElementById('the-audio');
const meterElement = document.getElementById('peak-meter');
const meterToggle = document.getElementById('meter-toggle');

const sourceNode = audioCtx.createMediaElementSource(audioElement);
sourceNode.connect(audioCtx.destination);

const buttonElement = document.getElementById('ctx-button');
buttonElement.addEventListener('click', () => {
  if (audioCtx.state === 'suspended') {
    audioCtx.resume();
  } else {
    audioCtx.suspend();
  }
});

const ctxStatus = document.getElementById('ctx-status');
setInterval(() => {
  ctxStatus.innerText = audioCtx.state;
  if (audioCtx.state === 'suspended') {
    buttonElement.innerText = 'Resume';
  } else {
    buttonElement.innerText = 'Suspend';
  }
}, 100);

let meterInstance = null;

meterToggle.addEventListener('click', () => {
  if (meterInstance) {
    meterInstance.cleanup();
    meterInstance = null;
    meterToggle.innerText = 'Create meter';
  } else {
    meterInstance = new webAudioPeakMeter.WebAudioPeakMeter(sourceNode, meterElement);
    meterToggle.innerText = 'Delete meter';
  }
});