问题简单描述：

<div class="helloTime">
      <ul class="hello_le">
       <li class="hello_le2">
        <c:if test="${user.identityId == 1}">
         <p class="hello_time">HI 厂家您好</p>
         <span class="welc">欢迎来到俱合网<span>
         </c:if>
        <c:if test="${user.identityId == 2}">
         <p class="hello_time">HI 买家您好</p>
         <span class="welc">欢迎来到俱合网<span>
         </c:if>
        <c:if test="${user.identityId == null}">
         <p class="hello_time" id="overTime">a</p>
         <span class="welc">欢迎来到俱合网<span>
         </c:if>
       </li>
       <li  class="hello_rig">
       <img class="xiaolu" src="${ctx}/common/images/titlelu1.png"> 
       </li>
      <ul>
     </div>

以下是js

(function(){
    var hh = document.getElementById("overTime");
    var now = new Date();
    var hours =now.getHours();
    if(hours>=12){
     hh.innerHTML = "HI,下午好";
    }else{
     hh.innerHTML ="HI,上午好";

    } 
})()

总是报错Uncaught TypeError: Cannot set property 'innerHTML' of null