I can do this manually using the following: Right-click on the video player, copy debug info, paste into text editor, and Ctrl+F for "addocid".

What is the best way to do this automatically?

By modifying an ad accelerator I found, I can reliably detect when a pre-roll ad is playing:

function handleVideoAd() {
	const video = document.querySelector('video');
	const adElement = document.querySelector('.video-ads.ytp-ad-module');
	if (video && adElement && adElement.children.length > 0) {
		alert('advertisement found!')
	}
}

function initializeAdHandling() {
	handleVideoAd();
	const observer = new MutationObserver(handleVideoAd);
	observer.observe(document.body, { childList: true, subtree: true });
}
initializeAdHandling()

If I had the video ID, I could then open the video in a new tab using something like:

window.open('https://www.youtube.com/watch?v=adVideoID');

However, I am at a bit of a loss as to how to extract the ad video ID itself.

In the browser inspector, the only places I can find the ad video ID are:

1. Within the URL for ytp-cued-thumbnail-overlay-image
2. As adVideoId within var ytInitialPlayerResponse, which itself is within <script nonce="rwc3vYf3vRLEyNQKsJOgig">, where rwc3vYf3vRLEyNQKsJOgig changes with every video.

What would be the best way to extract the advertisement video ID?

Apologies for if I'm going about this the wrong way. I am (very!) new to JavaScript, but interested in learning. Please let me know if I've broken any community rules, or committed any other sort of faux pas. Thanks! :)