JavaScript Tutorial

only-child

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>only-child demo</title>
  <style>
  div {
    width: 100px;
    height: 80px;
    margin: 5px;
    float: left;
    background: #b9e;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
    <div>
      <button>Sibling!</button>
      <button>Sibling!</button>
    </div>
    <div>
      <button>Sibling!</button>
    </div>
    <div>
      None
    </div>
    <div>
      <button>Sibling!</button>
      <button>Sibling!</button>
      <button>Sibling!</button>
    </div>
    <div>
      <button>Sibling!</button>
    </div>
    <script>
        $( "div button:only-child" ).text( "Alone" ).css( "border", "2px blue solid" );
    </script>
</body>
</html>