Get and Set Volume with JavaScript

The <audio> and <video> tags provide a wealth more functionality than most people know. For instance, did you know that you could detect supported video formats and audio formats using a few JavaScript tricks?  It got me to thinking about the possibilities of detecting system volume with JavaScript in the browser.

I hate to be a buzzkill but unfortunately JavaScript doesn't provide direct access to the system volume but you can, using <audio> and/or <video> elements, programmatically set and get the volume level.

// Getting volume level
const volume = document.querySelector("video").volume; // 1 

// Setting volume level
document.querySelector("video").volume = 0.5;  // set volume to 50%

You can also listen for volume changes with the "onvolumechange" event:

document.querySelector("video").addEventListener("onvolumechange", e => {
    // Change your custom control UI
});

It makes sense that you can't set system volume level from a random JavaScript snippet in a browser but I had a slight hope you could retrieve that level.  Setting volume with JavaScript for a given piece of media is relative to system volume level but hey -- at least we get to create custom controls for those elements with .volume settings!