Gerador de Youtube Embed

<!DOCTYPE html>
<html>
<head><title>Gerador de embed</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">
  <script>
    function createEmbed() {
      var value = document.getElementById("input").value;
      var embedCode = '<div class="embed-responsive embed-responsive-16by9">' +
        '<iframe class="embed-responsive-item" src="https://www.youtube.com/embed/' + value + '" allowfullscreen></iframe>' +
        '</div>';
      document.getElementById("output").value = embedCode;
    }
  </script>
</head>
<body>
  <div class="container">
      <br><br><br>
        <center>
<a href="#" class="btn btn-primary btn-lg " role="button" >Voltar ao início</a>
</center>
      <br><br><br>
    <div class="form-group">
      <label for="input">Informe o ID do Vídeo:<br>
      Exemplo em negrito -> https://youtu.be/<b>ql9O4AaxlZI</b></label>
      <input type="text" class="form-control" id="input" required>
    </div>
    <button onclick="createEmbed()" class="btn btn-primary">Gerar Embed</button>
    <br><br><br><br>


  <textarea id="output" name="output" class="form-control"></textarea>
  <br>


</form>
<br><br>


  </div>
</body>


</html>