使用JS获取SessionStorage的值

<script type="text/javascript">
    function login(){
      var username=window.document.getElementById("username").value;
      var password=window.document.getElementById("password").value;
      if(password=="123456")
      {
        window.sessionStorage.setItem("username", username);
        window.location.href="../index1.html" rel="external nofollow" ;
      }else{
        alert("密码错误请输入正确的密码，例如123456！");
        return false;
      }
    }
</script>
<input type="text" id="username" class="11" placeholder="请输入真实姓名"/>
<input type="password" id="password" placeholder="请输入密码（默认密码123456）"/>
<input type="button" value="登录考试" onclick="login()">

<script>
   $(function () {
     var username= window.sessionStorage.getItem("username")
     $("#yhm").html("登录用户"+username)
     $("#name").html(username)
     if(window.sessionStorage.getItem("username")===null){
       alert("您还没有登录，请登录后重试！")
       window.location.href="Pages/index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" ;
     }
     $("#esc").on("click",function(){
       window.sessionStorage.clear();
       window.location.href="Pages/index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" ;
     });
  })
 </script>

<div id="yhm"></div> 

<script>
$("#esc").on("click",function(){
       window.sessionStorage.clear();
       window.location.href="Pages/index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" ;
     });
</script>

<button id="esc" style="background-color: #FF0000">退出考试系统</button>