JSFiddle - React, Tailwind, and code Playground

HTML

<h3>
  Highlight and copy me!
</h3>
<p>
Just testing to see What hAppens.
</p>
<textarea placeholder="Paste here" rows="4" cols="50"></textarea>

SCSS

h3 {
  text-transform: uppercase;
}

JavaScript

$(document).on('copy', function(e){
  var sel = window.getSelection();
  var copiedText = sel.toString().toLowerCase().replace(/\b[a-z]/g, function(txtVal) { return txtVal.toUpperCase(); });
  var copyHolder = $('<div>', { html: copiedText, style: { opacity: '0' }});
  $('body').append(copyHolder);
  sel.selectAllChildren( copyHolder[0] );
  window.setTimeout(function() {
      copyHolder.remove();
  },0);
});