Prune All Archived Threads

// ==UserScript==
// @name Thread Watcher Pruner
// @namespace http://www.4chan.org/
// @match *://boards.4chan.org/*
// @match *://boards.4channel.org/*
// @grant none
// @run-at document-start
// ==/UserScript==

document.addEventListener('4chanMainInit', function(e) {
  let config = window.Config || window.FC.extConfig;
  if (!config.threadWatcher) return;
  ThreadWatcher.pruneArchivedThreads = function() {
    let w = ThreadWatcher.watched;
    let bl = ThreadWatcher.blacklisted;
    Object.keys(w).forEach(k => {
      // archived flag
      if (w[k].length > 3 && w[k][3]) {
        delete w[k];
        bl[k] = 1;
      }
    });
    ThreadWatcher.save();
    ThreadWatcher.build(true);
  };
  let addPruneLink = function(e) {
    let pruneLink = document.createElement('img');
    pruneLink.id = 'twRealPrune';
    pruneLink.alt = 'P';
    pruneLink.title = 'Prune';
    // behold the prune broom
    pruneLink.src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABIAAAASBAMAAACk4JNkAAAAElBMVEUBAAD///+5elcAAACDUTb+/v6YObyPAAAAAXRSTlMAQObYZgAAAGBJREFUeNo9jdERwCAMQnUDuU4g6QKaCdpzAfdfpjnUJj8cvIOEWdK6y/GrthW87Ti7HxUgDsgKFIGkE4pp3apMWrzMCINVT7fOIc/8frkayaFOMCwNZXA8azKT3Aox9wH5Rgw7swlc4wAAAABJRU5ErkJggg==';
    pruneLink.classList.add('pointer');
    pruneLink.classList.add('right');
    pruneLink.addEventListener('click', function() {
      ThreadWatcher.pruneArchivedThreads();
    });
    document.getElementById('twHeader').appendChild(pruneLink);
  };
  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', addPruneLink);
  } else {
    addPruneLink();
  }
});