JS菜鸟的问题，大虾帮帮忙

Question

你是不是方法名写错了？？<script>
function showwriteweek(){
  alert("good");
  document.getElementById("workplantype").value;
  alert("111");
  } </script>
<td width="13%" align="right" valign="top" bgcolor="#EEF4FF">
                <select name="workplantype11" id="workplantype" style="width:100%" onChange="showwriteweek();">
                  <option value="choose" selected>choose </option>
                  <option value="year" >aa </option>
                  <option value="season" >bb </option>
                  <option value="month">cc </option>
                  <option value="week">dd </option>
                </select>

Answer 1

<script>
function writeweekplan(){ 
  alert("good"); 
  var aa=document.getElementById("workplantype").value; 
  alert(aa); 
  } 
</script>
<td width="13%" align="right" valign="top" bgcolor="#EEF4FF"> 
                <select name="workplantype" id="workplantype" style="width:100%" onchange="showwriteweek();"> 
                  <option value="choose" selected>请选择 </option> 
                  <option value="year" >年工作计划 </option> 
                  <option value="season" >季工作计划 </option> 
                  <option value="month">月工作计划 </option> 
                  <option value="week">周工作计划 </option> 
                </select>
试试这个 你是不是要这个效果。select 取里面子项用onchange事件