Node.js与Mongoose参数查询用户触发ERR_INVALID_ARG_TYPE错误排查

我尝试通过URL参数按用户名查询数据库中的用户，已经编写了服务端、路由及控制器代码。当向..../users/gokdeniz（该用户在数据库中存在）发起GET请求时，触发TypeError [ERR_INVALID_ARG_TYPE]错误，错误提示res.send()接收了非法的函数类型参数。

现有代码 #

服务端代码 #

const express = require("express");
const mongoose = require("mongoose");
const app = express();

//ROUTES
const userRoute =require("./src/routes/userRoutes");
const postRoute =require("./src/routes/postRoutes");
const commentRoute =require("./src/routes/commentRoutes");

const port = process.env.PORT || 5000;

mongoose.connect("mongodb://localhost:27017/projectDB", {useNewUrlParser: true});

app.use(express.json());

app.use(express.urlencoded());

app.get("/", (req, res) =>{
    res.send("hello");
});

app.use("/", userRoute, postRoute, commentRoute);


app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`));

路由代码 #

const express = require('express');
const userRouter = express.Router();

const userController = require("../controllers/userController");


userRouter.route("/users/:userName")
.get(userController.getUser)
.patch(userController.updateUser)
.delete(userController.deleteUser)
.post(userController.newUser);

module.exports = userRouter;

控制器代码 #

const mongoose = require("mongoose");
const Users = require("../models/userModel");

module.exports.getUser = (req, res) => {
    console.log(req.params.userName);
    res.status(200).send(Users.find({name: req.params.userName}), (err, res)=>{
        if (res.err){
            console.log("USER NOT FOUND");
        }else{
            console.log("Success!");
        }
    });
};

错误信息 #

TypeError [ERR_INVALID_ARG_TYPE]: The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received type function ([Function (anonymous)])
    at new NodeError (node:internal/errors:371:5)
    at Function.from (node:buffer:322:9)
    at ServerResponse.send (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\response.js:193:22)
    at module.exports.getUser (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\src\controllers\userController.js:6:21)
    at Layer.handle [as handle_request] (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\route.js:144:13)      
    at Route.dispatch (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\route.js:114:3)
    at Layer.handle [as handle_request] (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\layer.js:95:5)
    at C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\index.js:284:15
    at param (C:\Users\tlege\OneDrive\Masaüstü\project 1\untitled_project\Server\node_modules\express\lib\router\index.js:365:14)

错误原因 #

控制器里的逻辑犯了两个关键错误：

1. 参数传递错误：Users.find()返回的是Mongoose的Query对象，不是查询结果，你直接把这个对象传给res.send()，还错误地把回调函数当成res.send()的第二个参数（res.send()只接受要返回的数据，不支持回调）。
2. 变量命名冲突：回调里用res作为第二个参数，覆盖了Express的响应对象res，导致后续逻辑完全混乱。

修复方案 #

推荐用async/await写法，代码更清晰易维护：

修复后的控制器代码（async/await版） #

const mongoose = require("mongoose");
const Users = require("../models/userModel");

module.exports.getUser = async (req, res) => {
    try {
        console.log(req.params.userName);
        // 按用户名查询用户，find返回数组，若只需单个用户可改用findOne
        const users = await Users.find({name: req.params.userName});
        
        if (users.length === 0) {
            console.log("USER NOT FOUND");
            return res.status(404).send("用户不存在");
        }
        
        console.log("Success!");
        res.status(200).send(users);
    } catch (err) {
        console.error("查询出错:", err);
        res.status(500).send("服务器内部错误");
    }
};

如果习惯用回调写法，修正后的代码如下：

修复后的控制器代码（回调版） #

const mongoose = require("mongoose");
const Users = require("../models/userModel");

module.exports.getUser = (req, res) => {
    console.log(req.params.userName);
    // 把回调函数放在find方法里，且避免变量名冲突
    Users.find({name: req.params.userName}, (err, users) => {
        if (err) {
            console.error("查询出错:", err);
            return res.status(500).send("服务器内部错误");
        }
        
        if (users.length === 0) {
            console.log("USER NOT FOUND");
            return res.status(404).send("用户不存在");
        }
        
        console.log("Success!");
        res.status(200).send(users);
    });
};

内容的提问来源于stack exchange，提问作者Bot Ellis