Node.js报错TypeError: res.setHeader is not a function求助

错误核心是变量名冲突：

• 路由回调里的res是Express框架的响应对象，具备setHeader、end等方法，用于向前端返回响应。
• 但你在http.get(url,(res) => {处使用了同名参数res，覆盖了外层的Express响应对象。此时内层的res是Node.js原生http模块的响应对象，它没有setHeader方法，所以执行到标注位置时触发TypeError。
• VSCode提示的“res已声明但未被读取”，正是因为外层的Expressres被内层同名变量覆盖，实际未被使用。

1. 重命名内层http.get的响应参数，避免覆盖外层Express的响应对象，比如改成httpRes。
2. 修复SQL插入语句的占位符错误：原语句INSERT INTO report(...) VALUES ()缺少占位符，需改为VALUES (?, ?, ?, ?, ?, ?)，否则插入操作会失败。
3. 完善错误处理：查询不到用户/设备、http请求失败等场景下，返回对应错误响应，避免请求长期挂起。

app.get("/gettemperature", (req, res) => {
    const email = req.query.email;

    //step1 get device ip from database using
    let stmt = `SELECT * FROM users WHERE email=?`;
    let todo = [email];
    console.log("email: "+email);
    
    db.query(stmt, todo, (err, results, fields) => {
      if (err) {
        console.error(err.message);
        return res.status(500).json({error: err.message});
      }

      if (results.length === 0) {
        return res.status(404).json({error: "用户不存在"});
      }

      let userid = results[0].id;
      console.log(userid);
      let getID = `SELECT * FROM controlModules WHERE deviceowner=?`;
      let getidData = [userid];

      db.query(getID, getidData, (err, results, fields) => {
        if (err) {
          console.error(err.message);
          return res.status(500).json({error: err.message});
        }

        if (results.length === 0) {
          return res.status(404).json({error: "未找到该用户的设备"});
        }

        const lanip = results[0].ipaddress;
        console.log(lanip);
        //step2 get temp where device ip
        //for local connection
        let url = "http://"+lanip+"/data";
        // 重命名内层res为httpRes，避免覆盖外层Express的res
        http.get(url,(httpRes) => {
          let body = "";
  
          httpRes.on("data", (chunk) => {
              body += chunk;
          });
  
          httpRes.on("end", () => {
              try{
                  let json = JSON.parse(body);
                  const temperature = json.temperature.value;
                  const humidity = json.humidity.value;
                  const waterlevel = "";
                  const nutrient = "";

                  console.log(temperature);

                  let date_ob = new Date();
                  let date = ("0" + date_ob.getDate()).slice(-2);
                  let month = ("0" + (date_ob.getMonth() + 1)).slice(-2);
                  let year = date_ob.getFullYear();
                  let hours = date_ob.getHours();
                  let minutes = date_ob.getMinutes();
                  let seconds = date_ob.getSeconds();
                  const dateStamp = month+"/"+date+"/"+year+" "+hours+":"+minutes

                  if(lanip != ""){
                    //getting parentid
                        console.log(userid);
                        // 修复SQL占位符错误
                        let inserreport = `INSERT INTO report(date,farm,temperature,humidty,waterlevel,nutrientsolutionlevel) VALUES (?, ?, ?, ?, ?, ?)`;
                        let inserreportval = [dateStamp,userid,temperature,humidity,waterlevel,nutrient];
                        
                        //inserting to childtable
                        db.query(inserreport, inserreportval, (err, data, fields) => {
                          if (err) {
                            console.error(err.message);
                            return res.status(500).json({error: err.message});
                          }

                          //success inserting to table then get inserted data
                            console.log(userid);
                            let getreport = `SELECT * FROM report WHERE farm=?`;
                            let getreportval = [userid];
                            console.log("getreportval "+getreportval);

                            //getting report list
                            db.query(getreport, getreportval, (err, results, fields) => {
                              if (err) {
                                console.error(err.message);
                                return res.status(500).json({error: err.message});
                              }
                              let data = [];
                              for(let i = 0; i < results.length; i++){
                                data.push({
                                  date: results[i].date,
                                  temperature: results[i].temperature,
                                });
                              }

                              // 现在使用的是外层的Express响应对象res，可正常调用方法
                              res.setHeader("Content-Type", "application/json");
                              res.writeHead(200);
                              res.end(JSON.stringify(data,null,3));
                            });
                          
                        });
                  }
              }catch(error) {
                  console.error(error.message);
                  return res.status(500).json({error: error.message});
              };
          });
  
      }).on("error", (error) => {
          console.error(error.message);
          return res.status(500).json({error: "获取设备数据失败: " + error.message});
      });
        //end of step2
      });
    });
});

内容的提问来源于stack exchange，提问作者Ian Ducao