selection-range-5

<!doctype html>
<body>
<p id="p">Select me: <i>italic</i> and <b>bold</b></p>

From <input id="from" disabled> – To <input id="to" disabled>
<script>
  document.onselectionchange = function() {
    let {anchorNode, anchorOffset, focusNode, focusOffset} = document.getSelection();

    from.value = `${anchorNode && anchorNode.data}:${anchorOffset}`;
    to.value = `${focusNode && focusNode.data}:${focusOffset}`;
  };
</script>
</body>