错误，而使用deleteOne在app.delete函数在Node.js

Question

**尝试使用app.delete并尝试使用删除一从mondo db删除文档...它不断抛出错误。如何解决这个错误？** ``` 需要（'dotenv'）. config（）const Express=要求（'Express'）const app=Express（）const PORT=process.env.PORT||5001 const ConnectDB=要求（'./config/db'）const errorHandler=要求（'./middleware/error'）const Products=需要（'。/模型/产品'）const cors=需要（'cors'）

    // Connect DB
    connectDB()
    
    
    // Middleware
    app.use(cors())
    app.use(express.json())
    app.use('/auth', require('./routes/authRoutes'))
    app.use('/admin', require('./routes/adminRoutes'))
    app.use('/customer', require('./routes/customerRoutes'))
    app.use('/staff', require('./routes/staffMemberRoutes'))
    // error handler - should be *last* piece of middleware
    app.use(errorHandler)
    
    
    app.get('/all-products', (req, res) => {
      Product.find({}, (error, posts) => {
        if(error) {
          res.json({error: 'Unable to fetch products!'}) 
        } else {
          res.json(posts)
        }
      })
    })
    
    
    
    app.post ('/add-products',(req,res) =>{
      console.log("add-products has been fired")
      const imageurl = req.body.imageurl 
      const title = req.body.title
      const description = req.body.description 
      const rate = req.body.rate 
      const category = req.body.category 
      const subcategory = req.body.subcategory 
    
      let product  = new Product({
        imageurl: imageurl,
        title: title,
        description: description,
        rate: rate,
        category: category,
        subcategory: subcategory,
      })
    
    
      product.save((error) => {
        if(error) {
          res.json({error: 'Unable to save the product!'})
        } else {
          res.json({success: true, message: 'New product Saved'})
        }
      })
    
    })
    
    
    
    app.delete('/product/:productId', (req, res) => {
    
      const productId = req.params.productId 
    
      Product.deleteOne({
        _id: productId
      }, (error, result) => {
        if(error) {
          res.json({error: 'Unable to delete product'})
        } else {
          res.json({success: true, message: 'Product deleted successfully!'})
        }
      })
    
    })
    
    
    
    app.put('/update-product/:productId', (req, res) => {
    
      const productId = req.params.productId 
      const imageurl = req.body.imageurl 
      const title = req.body.title
      const description = req.body.description 
      const rate = req.body.rate 
      const category = req.body.category 
      const subcategory = req.body.subcategory 
    
      const updatedProduct = {
        imageurl: imageurl,
        title: title,
        description: description,
        rate: rate,
        category: category,
        subcategory: subcategory,
      }
    
      Product.findByIdAndUpdate(productId, updatedProduct, (error, result) => {
          if(error) {
              res.json({error: 'Unable to updated the Product'})
          } else {
              res.json({success: true, message: 'Product updated successfully!'})
          }
      })
    
    })
    
    
    const server = app.listen(PORT, () => {
      console.log(`Server running on port ${PORT}`)
    })
    
    // makes giant server errors concise and simple to read
    process.on('unhandledRejection', (err, promise) => {
      console.log(`Logged Error: ${err}`)
      server.close(() => process.exit(1))
    })```

Answer 1

if(error) {
      res.json({error: 'Unable to delete product'})
    }

在这一行中，将res.json替换为：

res.json({error})

然后在此处注释输出（控制台上的错误消息）