JSFiddle - React, Tailwind, and code Playground

HTML

<table id="diff_table">
      <tr>
        <td class="added"><span>Some text in this cell ...</span></td>
      </tr>
    </table>

CSS

.diff-select {
      color: blue;
    }
Some text in this cell ...

JavaScript

function selectPre(b) {
            var s;                               // added - selection variable
            var e = b.parentNode.nextSibling;    // added - parent sibling element
            
            if (window.getSelection) {
                var s = window.getSelection();
                if (s.setBaseAndExtent) {
                    s.setBaseAndExtent(e, 0, e, e.innerText.length - 1);
                }
                else {
                    var r = document.createRange();
                    r.setStart(e.firstChild, 0);
                    r.setEnd(e.lastChild, e.lastChild.textContent.length);
                    s.removeAllRanges();
                    s.addRange(r);
                }
            }
            else if (document.getSelection) {
                var s = document.getSelection();
                var r = document.createRange();
                r.selectNodeContents(e);
                s.removeAllRanges();
                s.addRange(r);
            }
            else if (document.selection) {
                var s = document.body.createTextRange();
                s.moveToElementText(e);
                s.select();
            }
            
            // added - copy and change button text
            if (s) {
                try {
                    var successful = document.execCommand('copy');
                    // var msg = successful ? 'successful' : 'unsuccessful';
                    // console.log('Copying text command was ' + msg);
                    if (successful) {
                        b.innerHTML = "Copied";
                    }
                } catch (err) {
                    // console.log('Oops, unable to copy');
                }
            }
        }

        var diff = document.getElementById('diff_table').getElementsByTagName('tr');
        var difflen = diff.length;
        for(i=0; i<difflen; i++) {
            var newdiff = diff[i].childNodes[1];          
            if (newdiff.className &&...