如何解决“ Router.use（）需要中间件功能，但在Function.use获得对象”错误

Question

I am getting an error when calling my router from my routes directory.I have made some changes in my code around some of the other posts on this issue but I can't get anything to solve.However i am not sure what exactly is wrong with my code below.

This is my error

[nodemon] restarting due to changes...
[nodemon] starting `node app.js`
E:\Program Files\mean apps\shoppinglist\crud-backend\node_modules\express\lib\router\index.js:458
      throw new TypeError('Router.use() requires a middleware function but got a ' + gettype(fn))
      ^

TypeError: Router.use() requires a middleware function but got a Object
    at Function.use (E:\Program Files\mean apps\shoppinglist\crud-backend\node_modules\express\lib\router\index.js:458:13)
    at Function.<anonymous> (E:\Program Files\mean apps\shoppinglist\crud-backend\node_modules\express\lib\application.js:220:21)
    at Array.forEach (<anonymous>)
    at Function.use (E:\Program Files\mean apps\shoppinglist\crud-backend\node_modules\express\lib\application.js:217:7)
    at Object.<anonymous> (E:\Program Files\mean apps\shoppinglist\crud-backend\app.js:42:5)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:279:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:752:3)
[nodemon] app crashed - waiting for file changes before starting...

I have this code in my app.js

//importing  modules
var express = require('express');

var mongoose = require('mongoose');
var bodyparser = require('body-parser');
var cors = require('cors');
var path = require('path');

var app = express();

const route = require('./routes/route');

//conect to the mongodb
mongoose.connect('mongodb://localhost:27017/shoppinglist');

//on connection
mongoose.connection.on('connected',()=>{
    console.log('Connected to database mongodb @ 27017');
});

//error
mongoose.connection.on('error',(err)=>{
    if(err)
    {
        console.log('Error in database connection:'+ err);
    }  
});

//port no
const port = 3000;

//adding middleware - cors
app.use(cors());

//body - parser
app.use(bodyparser.json());

//static files
app.use(express.static(path.join(__dirname, 'public')));

//routes
app.use('/api', route);

//testing server
app.get('/',(req, res)=>{
    res.send('foobar');
});

app.listen(port,()=>{
    console.log('Server started at port:' + port);
});

I have this code in my route.js

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

const Item = require('../model/shoppingItem');

//retriving data from db
router.get('/items', (req, res, next)=>{
    Item.find(function(err, items){
        if(err){
            res.json(err);
        }
        else{
            res.json(items);
        }
    });
});

//insert data 
router.post('item', (req, res, next)=>{
    let newShoppingItem = new Item({
        itemName: req.body.itemName,
        itemQuantity: req.body.itemQuantity,
        itemBought: req.body.itemBought
    });
    newShoppingItem.save((err, item)=>{
        if(err){
            res.json(err);
        }
        else{
            res.json({msg: 'Item has been added successfully'});
        }
    });
});

Answer 1

You are using a module that you never exported.

app.use('/api', route);

but route was never exported - that's your main issue.

in your route module you can wrap everything in export default - alternatively you can use module.exports = router

This is an open source project I was working on try following the structure, if you still have issues let me know.

https://github.com/Muhand/nodejs-server