应用程序中未定义参考错误

Question

尝试在表单上提交数据时，网络服务器给我一个错误，说Reference error: Item is not defined，但根据我的代码，一切看起来都不错。在我的代码中是否有任何对您来说很突出的东西可能导致这种情况？我在玩 Const，但我不确定这是否是问题所在。这是我的 Javascript 文件：const express = require('express');const app = express();const bodyParser  = require('body-parser');const mongoose = require('mongoose');//specify where to find the schemaconst Items = require('./models/item')// connect and display the status mongoose.connect('mongodb://localhost:27017/items', { useNewUrlParser: true, useUnifiedTopology: true })  .then(() => { console.log("connected"); })  .catch(() => { console.log("error connecting"); });// use the following code on any request that matches the specified mount pathapp.use((req, res, next) => {   console.log('This line is always called');   res.setHeader('Access-Control-Allow-Origin', '*'); //can connect from any host   res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, OPTIONS'); //allowable methods   res.setHeader('Access-Control-Allow-Headers', 'Origin, Content-Type, Accept');   next();});app.get('/items', (req, res, next) => {  //call mongoose method find (MongoDB db.Items.find())  Items.find()    //if data is returned, send data as a response     .then(data => res.status(200).json(data))    //if error, send internal server error    .catch(err => {      console.log('Error: ${err}');      res.status(500).json(err);    });});  // parse application/x-www-form-urlencodedapp.use(bodyParser.urlencoded({ extended: false }))// parse application/jsonapp.use(bodyParser.json())// serve incoming post requests to /itemsapp.post('/items', (req, res, next) => {// create a new item variable and save request’s fields const Items = new   items ({  itemName: req.body.itemName,  servings: req.body.servings});//send the document to the database Items.save()  //in case of success  .then(() => { console.log('Success');})  //if error  .catch(err => {console.log('Error:' + err);});  });//to use this middleware in other parts of the applicationmodule.exports=app;

Answer 1

app.post('/items', (req, res, next) => {

// Items already defined

const items = new Items({

  itemName: req.body.itemName,

  servings: req.body.servings

});

items.save()

  //in case of success

  .then(() => { console.log('Success');})

  //if error

  .catch(err => {console.log('Error:' + err);});

  });

Items 常量已被声明，而您试图重新声明它