对这件事还不熟悉，似乎找不到这个问题的答案。首先，下拉菜单呈现给ejs模板。我正在尝试让第二个下拉列表根据第一个下拉列表的选择进行更新。我可以调用ajax并将值放到第二个下拉列表中。填充第二个下拉列表的mysql查询是硬编码的，我需要找到一种动态的方法。查询结果需要根据html下拉选项进行更改
应用程序.js

var express = require("express");
var app = express();
var mysql = require("mysql");
var path = require('path');

app.set("view engine","ejs");
var bodyParser = require("body-parser");
app.use(bodyParser.urlencoded({extended: true}));
app.use(express.static("public"));
var con;

app.get("/",function(req,res){
con.query("SELECT DISTINCT category FROM gameinfo",function(err,result){
      if(err) throw err;
      res.render('home',{result:result});
  });
});
//**part it says "3pk" needs to be dynamic**
app.get("/test",function(req,res){
  con.query("SELECT DISTINCT gamename FROM gameinfo WHERE category ='3PK'",function(err,result){
      if(err) throw err;
      res.send(result);

  });
});

home.ejs文件

<select name ="newCategoryD" id ="catSelection">
        <% for (var i = 0; i < result.length; i++){ %>
            <option>
                <%=result[i].category %>
            </option>
        <% } %>
    </select>
    <button id = "categoryBox">select this</button>

 <br></br>
 <div>
     <select id="games" ></select>
 </div>

 <script>
    $(document).ready(function(){
    $('#categoryBox').click(function(){
        $.ajax({
           type:'GET',
           url:'/test',
           dataType:'json',
          success: function(data){
              $('#games').empty();
            for (var i = 0; i < data.length; i++){
                $('#games').append('<option>'+data[i].gamename+'</option>')
            }

          }        
});

 });
 });

 </script>

非常感谢您的帮助