w3css 在线编辑器 | w3css代码测试

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.cainiaomax.com/w3css/4/w3.css">
<body>
<div class="w3-container">

<h2>Active 手风琴</h2>
<p>在本例中，我们将 w3-red 类添加到活动手风琴中（当单击按钮并打开内容时）。</p>

<button onclick="myFunction('Demo2')" class="w3-button w3-block w3-black w3-left-align">打开第 2 节</button>
<div id="Demo2" class="w3-hide w3-container">
    <p>其他一些文字..</p>
</div>

</div>
<script>
function myFunction(id) {
  var x = document.getElementById(id);
  if (x.className.indexOf("w3-show") == -1) {
    x.className += " w3-show";
    x.previousElementSibling.className = 
    x.previousElementSibling.className.replace("w3-black", "w3-red");
  } else { 
    x.className = x.className.replace(" w3-show", "");
    x.previousElementSibling.className = 
    x.previousElementSibling.className.replace("w3-red", "w3-black");
  }
}
</script>

</body>
</html>

报个问题: