howto 在线编辑器 | howto代码测试

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>body {
  font-family: "Lato", sans-serif;
  transition: background-color .5s;
}

.sidenav {
  height: 100%;
  width: 0;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: #111;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 60px;
}

.sidenav a {
  padding: 8px 8px 8px 32px;
  text-decoration: none;
  font-size: 25px;
  color: #818181;
  display: block;
  transition: 0.3s;
}

.sidenav a:hover {
  color: #f1f1f1;
}

.sidenav .closebtn {
  position: absolute;
  top: 0;
  right: 25px;
  font-size: 36px;
  margin-left: 50px;
}

#main {
  transition: margin-left .5s;
  padding: 16px;
}

@media screen and (max-height: 450px) {
  .sidenav {padding-top: 15px;}
  .sidenav a {font-size: 18px;}
}
</style>
</head>
<body>

<div id="mySidenav" class="sidenav">
  <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
  <a href="#">About</a>
  <a href="#">Services</a>
  <a href="#">Clients</a>
  <a href="#">联系方式</a>
</div>

<div id="main">
  <h2>侧边导航推送示例</h2>
  <p>单击下面的元素打开侧边导航菜单，并将此内容推到右侧。 请注意，当 sidenav 打开时，我们向 body 添加了黑色透明背景色。</p>
  <span style="font-size:30px;cursor:pointer" onclick="openNav()">&#9776; open</span>
</div>

function closeNav() {
  document.getElementById("mySidenav").style.width = "0";
  document.getElementById("main").style.marginLeft= "0";
  document.body.style.backgroundColor = "white";
}
</script>
   
</body>
</html>

报个问题: