Will search and mark duplicated IDs on a page #bookmarklet

find-duplicated-ids.js

javascript: void ((function() {
  /* More bookmarklets at https://gist.github.com/iamandrewluca/61feacf07bc4f2f50e70f986c2e9b2d2 */
  document.querySelectorAll('[id]').forEach(el => {
    const specificIds = document.querySelectorAll(`[id="${el.id}"]`);
    if (specificIds.length > 1 && specificIds[0] === el) {
      console.log('Duplicate id ' + el.id);
      specificIds.forEach(element => {
        element.style.outline = '5px solid red';
      });
      alert('duplicate found');
    }
  });
})());