Copy (CTRL + C) com JavaScript

## index.html
<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>

  <input id="text" />

  <button id="copy">Copy</button>

  <script type="text/javascript">
    const textInput = document.getElementById('text');
    const copyButton = document.getElementById('copy');

    copyButton.addEventListener('click', ()=> {
      textInput.select();
      document.execCommand('copy');
    });
  </script>

</body>
</html>