open-links-in-new-tab.js

gistfile1.js

<script type="text/javascript">
jQuery(document).ready(function($){
  $('a').each(function(){
     const href = $(this).attr('href');
     if (!href) {
        return;
     }
     const isNotAnchor = href.indexOf('#') === -1;
     const isNotInternalLink = href.indexOf('YOUR_WEBSITE_URL') !== 0 && href.indexOf('/') !== 0;

     if (isNotAnchor && isNotInternalLink) {
        $(this).attr('target', '_blank');
      }
   });
});
</script>