This code is a **Tampermonkey user script** that manipulates YouTube's...

This code is a Tampermonkey user script that manipulates YouTube's interface by performing the following actions:

1. Title and Metadata:

   • The script is named "YouTube Feed Manipulator (8× Repeat)".
   • It works on YouTube desktop (https://www.youtube.com/*) and YouTube mobile (https://m.youtube.com/*).
   • The stated purpose is to shuffle YouTube feed items and mark specific videos as 'watched', with the last two video IDs repeated 8 times (total).

2. Code Behavior:

   Here's a breakdown of what the script does:

   a) Base Video IDs:

   • An array called baseWatched contains several video IDs, which represent videos to be marked as "watched".

   const baseWatched = [
       '65k8VIyJlXQ',
       'q5-b7v6EIzc',
       'gaBBZshLhMY',
       ...
   ];
   

   b) Repetition of the Last Two Video IDs:

   • The last two IDs in the baseWatched array are extracted and repeated 8 times (including their original occurrences). This creates a new array watchedVideos containing all video IDs.

   const lastTwo = baseWatched.slice(-2); // Last two IDs
   for (let i = 0; i < 7; i++) {
       watchedVideos.push(...lastTwo);  // Add last two IDs 7 more times
   }
   

   c) Extract Video ID from a YouTube URL:

   • The extractVideoIdFromUrl function extracts the v parameter (video ID) from a YouTube URL if present.

   function extractVideoIdFromUrl(url) {
       const m = url.match(/[?&]v=([^&#]+)/);
       return m ? m[1] : null;
   }
   

   d) Shuffle YouTube Feed:

   • The function shuffleFeed shuffles the video feed displayed on YouTube using the Fisher–Yates shuffle algorithm.
   • It identifies YouTube grid elements (ytd-rich-grid-media, ytd-video-renderer, etc.), shuffles their order, and appends shuffled elements back to the grid.

   function shuffleFeed() {
       const grid = document.querySelector('ytd-rich-grid-renderer .rich-grid-renderer');
       const items = Array.from(grid.children).filter(/* filter video elements */);
       for (let i = items.length - 1; i > 0; i--) {
           const j = Math.floor(Math.random() * (i + 1));
           [items[i], items[j]] = [items[j], items[i]];  // Swap items
       }
       items.forEach(item => grid.appendChild(item));  // Re-append shuffled
   }
   

   e) Mark Videos as 'Watched':

   • The markSpecifiedVideosAsWatched function scans the videos on the page and checks their IDs against the watchedVideos array.
   • If a video ID matches one in the array, it adds a CSS class (.watched-video) to the corresponding element, visually marking it as watched.

   function markSpecifiedVideosAsWatched() {
       const videos = document.querySelectorAll(
           'ytd-rich-grid-media, ytd-video-renderer, ytd-grid-video-renderer'
       );
       videos.forEach(videoEl => {
           const id = extractVideoIdFromUrl(a.href);
           if (watchedVideos.includes(id)) {
               videoEl.classList.add('watched-video');
           }
       });
   }
   

   f) Styling Watched Videos:

   • The script dynamically adds CSS rules to the page to style .watched-video elements. These videos are made semi-transparent (opacity: 0.5) and outlined with a border.

   const css = `
   .watched-video {
       opacity: 0.5 !important;
       border: 2px solid #ccc;
   }`;
   

   g) Combine and Run on Page Load:

   • When the page loads, the script waits 1.5 seconds before executing:
     1. shuffleFeed() shuffles the grid of displayed videos.
     2. markSpecifiedVideosAsWatched() marks specific videos in the grid as "watched".

   window.addEventListener('load', () => {
       setTimeout(() => {
           shuffleFeed();
           markSpecifiedVideosAsWatched();
       }, 1500);
   });
   

3. Summary of Functionality:

• Shuffles YouTube feed videos: Randomly rearranges the videos in the main feed using the Fisher–Yates shuffle.
• Marks videos as 'watched': Adds visual indicators (semi-transparent effect and border) to videos based on their video IDs.
• Repetition of video IDs: Ensures that the last two videos in the original list are processed 8 times in total when marking them as watched.