document.addEventListener("DOMContentLoaded", function() { let headerRow = document.querySelector('.tribe-events-calendar-list__header-row'); if (!headerRow) return; // voorkom dubbel toevoegen if (headerRow.querySelector('.custom-aanmelden-header')) return; let div = document.createElement('div'); div.className = 'custom-aanmelden-header'; div.innerText = 'Aanmelden'; headerRow.appendChild(div); });