Amplify audio/video source Javascript

amplify.js

function amplify(node, gain) {
  const audioCtx = new AudioContext();
  const source = audioCtx.createMediaElementSource(node);

  // create a gain node
  const gainNode = audioCtx.createGain();
  gainNode.gain.value = gain;
  source.connect(gainNode);

  // connect the gain node to an output destination
  gainNode.connect(audioCtx.destination);
}

amplify.min.js

function amplify(node,gain){const audioCtx=new AudioContext();const source=audioCtx.createMediaElementSource(node);const gainNode=audioCtx.createGain();gainNode.gain.value=gain;source.connect(gainNode);gainNode.connect(audioCtx.destination)}

Nice work @matiaslopezd
However, if the line amplify(document.querySelector('video')); gets executed more than one time it will generate an error saying,

Uncaught InvalidStateError: Failed to execute 'createMediaElementSource' on 'AudioContext': HTMLMediaElement already connected previously to a different MediaElementSourceNode.

We can work around the issue by tweaking the function a bit.

function amplify(node, gain = 2) {
  // Reuse existing AudioContext if available
  if (!node._audioCtx) {
    node._audioCtx = new AudioContext();
    node._sourceNode = node._audioCtx.createMediaElementSource(node);
    node._gainNode = node._audioCtx.createGain();

    node._sourceNode.connect(node._gainNode);
    node._gainNode.connect(node._audioCtx.destination);
  }

  // Just update gain
  node._gainNode.gain.value = gain;
}

With the updated code in place, the volume can be adjusted dynamically at any time by invoking the function in the browser console.
e.g.

amplify(document.querySelector('video'), 2); // increase 
amplify(document.querySelector('video'), 0.5); // decrease

@Saiful-Islam-Sakib thank you! I wrote this before I discovered the extension Volume Master. In my opinion, just use the extension 😄

@Saiful-Islam-Sakib thank you! I wrote this before I discovered the extension Volume Master. In my opinion, just use the extension 😄

There's no doubt the extension is great, but I prefer using the code instead I’d rather not have any extensions running in the background 😅
Btw thanks.