Trigger custom events in Google Analytics, using script containing gtag

Question

Im trying to create a script that sends custom events to GA, whenever visitors click on certain links - in this case all 'tel:' links.

But no events are getting fired in my script atm - and I'm getting a "keep alive" error.

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=-UA-1234567-89"></script>
<script type="text/javascript">
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', 'UA-1234567-89');

jQuery("a[href^='tel']").on('click', function (){
    gtag('event', 'klik', {
      'event_category': 'mobil_opkald',
    });
});
</script>

Any help is greatly appreciated!