Removes events matching the given RegExes from the event calendar's sidebar, optionally preserving the first matching event.

tkoaly-events-blocklist.user.js

// ==UserScript==
// @name     TKO-äly Event Calendar Blocklist
// @version  1
// @grant    none
// @include  https://members.tko-aly.fi/
// ==/UserScript==

const members = [
  { pattern: /chess/, keepFirst: true },
  { pattern: /liikuntavuoro/, keepFirst: true },
  { pattern: /Board Game Weekly/, keepFirst: true },
];

const seen = new Array(BLOCKLIST.length).fill(false);

const events = document.querySelectorAll('#events_menu .event');

[...events].forEach((el) => {
  let matches = false;
  
  BLOCKLIST.forEach(({ pattern, keepFirst }, i) => {
  	const match = el.innerText.match(pattern);
    
    if (match && (!keepFirst || seen[i])) {
      matches = true;
    }
    
    if (match) {
      seen[i] = true;
    }
  });
  
  if (matches) {
    el.style.display = 'none';
    el.nextElementSibling.style.display = 'none';
  }
});