Filer Select2 with several criteria

Limit Select2 items according to other criteria.

by Bruno G.

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/css/select2.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/js/select2.js"></script>
<select id="sel">

JavaScript

(function() {
 /* var ops = [
    {'text': 'Group 1', "children" : [
        {"id": 1,"text": "Option 1.1"},
        {"id": 2,"text": "Option 1.2"}
      ]
    },
    {"text": "Group 2", "children" : [
        {"id": 3,"text": "Option 2.1"},
        {"id": 4,"text": "Option 2.2"}
      ]
    }
  ];*/
var ops = [{"text":"Governments","children":[{"text":"House of Commons - Canada","id":"www.ourcommons.ca","langs":"en-fr,fr-en"},{"text":"MEES","id":"education.gouv.qc.ca","langs":"en-fr,fr-en"},{"text":"European Commission","id":"ec.europa.eu","langs":"en-fr,fr-en,en-es,es-en,fr-es,fr-es,en-ru"}]},{"text":"Legal - Regulations","children":[{"text":"CanLII","id":"canlii.org","langs":"en-fr,fr-en"},{"text":"SEDAR","id":"www.sedar.com","langs":"en-fr,fr-en"},{"text":"Fintrac","id":"fintrac-canafe.gc.ca","langs":"en-fr,fr-en"},{"text":"Autorit\u00e9 des march\u00e9s financiers","id":"lautorite.qc.ca","langs":"en-fr,fr-en"},{"text":"International Court of Justice","id":"icj-cij.org","langs":"en-fr,en-es,es-en,fr-en,fr-es,es-fr"},{"text":"European Court of Human Rights","id":"www.echr.coe.int","langs":"en-fr,fr-en"},{"text":"IIROC-OCRCVM","id":"iiroc.ca","langs":"en-fr,fr-en"},{"text":"OSFI-BSIF","id":"www.osfi-bsif.gc.ca","langs":"en-fr,fr-en"}]},{"text":"Health - Life Science","children":[{"text":"World Health Organization","id":"www.who.int","langs":"en-fr,fr-en,en-es,es-en,en-ar,ar-en,en-zh,zh-en,en-ru,ru-en"},{"text":"European Medicines Agency","id":"www.ema.europa.eu","langs":"en-fr,fr-en,en-es,es-en"},{"text":"Cochrane","id":"www.cochrane.org","langs":"en-fr,fr-en,en-es,es-en,en-de,de-en"}]},{"text":"Transport","children":[{"text":"International Civial Aviation Organization","id":"www.icao.int","langs":"en-fr,fr-en,en-es,es-en,en-ar,ar-en,en-zh,zh-en,en-ru,ru-en"},{"text":"NAV Canada","id":"www.navcanada.ca","langs":"en-fr,fr-en"},{"text":"International Maritime...