View text source at Wikipedia
if (mw.config.get('wgAction') == "history") { // Make sure we're on a History page. Otherwise, it's just stupid.
// Grab default Watchers link and clone it
var activeWatchLink = $("[href*='#mw-pageinfo-watchers']");
var activeWatchLinkClone = activeWatchLink.clone(true);
// Change original Watchers link display
activeWatchLink.before("Number of watchers: ");
activeWatchLink.text("All");
// Set new Watchers link URL, text, and tooltip
activeWatchLinkClone.attr('href', 'http://toolserver.org/~dispenser/cgi-bin/watcher.py?page=' + mw.config.get('wgPageName'));
activeWatchLinkClone.text('Active');
activeWatchLinkClone.attr('title', 'Check the number of users watching this page who have logged in within the last 30 days');
// Place constructed link after the original Watchers link, add bullet
activeWatchLinkClone.insertAfter(activeWatchLink);
activeWatchLinkClone.before(' <b>/</b> ');
}