老师请问为什么点击按钮后取不到值

来源：2-8 自由编程

TOUU_JP

2020-10-04 16:09:45

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style>
</style>
</head>
<body>
   <form aciton="em">
       <input type="button" value="员工列表" name="inout" style="width: 500px">
       <input type="button" value="职位列表" name="inout" style="width: 500px">
       <input type="button" value="部门列表" name="inout" style="width: 500px">
       <div id="div" name="employee"></div>
   </form>
   <script type="text/javascript">
       var input = document.getElementsByName("inout");
       for (var a = 0; a < input.length; a++) {
           input[a].onclick = function() {
               //xmlHttpRequest作成
               var xmlHttp;
               if (window.XMLHttpRequest) {
                   xmlHttp = new XMLHttpRequest();
               } else {
                   xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
               }
               //HTTPsend
               xmlHttp.open("GET", "/EmployeeList/EmployeeList", true);
               xmlHttp.send();
               //Response処理
               xmlHttp.onreadystatechange = function() {
                   if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
                       var tex = xmlHttp.responseText;
                       var json = JSON.parse(tex);
                       console.log(json);
                       document.getElementById("div").innerHTML = json[a];
                   }
               }
           }
       }
   </script>
</body>
</html>

package com.immoc.ajax;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.alibaba.fastjson.JSON;

/**
* Servlet implementation class EmployeeList
*/
@WebServlet("/EmployeeList")
public class EmployeeList extends HttpServlet {
   private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public EmployeeList() {
        super();
        // TODO Auto-generated constructor stub
    }

   /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       List list = new ArrayList();
       list.add("小红<br>小明<br>小白");
       list.add("职员<br>经理");
       list.add("人事部<br>技术部<br>无线事业部");
       String json = JSON.toJSONString(list);
       response.setContentType("text/html;charset=UTF-8");
       response.getWriter().println(json);
   }

}