嘗試使用空輸入欄位提交時React應用程式崩潰

請幫助我解決這個問題，因為我搜索了所有互聯網但找不到答案:(

我正在使用 MERN Stack 制作網站，但遇到了一個問題：

每當我在空的輸入欄位上單擊更新時，我的應用程式就會崩潰。

當我在 Axios 更新請求中捕獲錯誤時，它只是顯示Network Error。

我想問一下有沒有辦法解決這個錯誤？也許如果輸入欄位為空，更新按鈕不會觸發？

這是我的代碼：

// DinnerIdeas.js
import React, { useState, useEffect } from "react"
import './DinnerIdeas.css'
import Axios from "axios"

import FoodListComponent from "../FoodListComponent";
import FormComponent from "../FormComponent";

function DinnerIdeas() {

    const [foodName, setFoodName] = useState('')
    const [isVegetarian, setVegetarian] = useState(false)
    const [priceRange, setPriceRange] = useState('$')
    const [newFoodName, setNewFoodName] = useState(null)
    const [foodList, setFoodList] = useState([])
  
    // Read:
    useEffect(() => {
      let unmounted = false
      Axios.get("http://localhost:3001/read")
      .then((response) => {
        if (!unmounted) {
          setFoodList(response.data)
        }
      })
      .catch(error => {
        console.log(`Hey, the error is ${error}`)
        return
      })
      return () => {
        unmounted = true
      }
    }, [foodList])
  
    // Create:
    const addToList = () => {
      Axios.post(
        "http://localhost:3001/insert", 
        {
          foodName: foodName,
          isVegetarian: isVegetarian,
          priceRange: priceRange,
        }
      )
    }
  
    // Update:
    const updateFood = (id) => {
      Axios.put("http://localhost:3001/update", {
        id: id,
        newFoodName: newFoodName,
      })
      .catch(error => console.log(`Hey, the error is ${error}`))
    }
  
    // Delete:
    const deleteFood = (id) => {
      Axios.delete(`http://localhost:3001/delete/${id}`)
    }
    
    return (
      <section className="dinner-ideas">
        <FormComponent
          setFoodName={setFoodName}
          setVegetarian={setVegetarian}
          setPriceRange={setPriceRange}
          addToList={addToList}
        />
        <FoodListComponent 
          foodList={foodList} 
          setNewFoodName={setNewFoodName}
          updateFood={updateFood} 
          deleteFood={deleteFood}
        />
      </section>
    );
  }
  
  export default DinnerIdeas;

表單組件：

export default function FormComponent(props) {
    return (
        <div className="dinner container">
            <h1 className="dinner--title">Dinner Ideas</h1>
            <form>
                <div className="form-group">
                    <label htmlFor="name">Food name:</label>
                    <input
                        type="text"
                        name="name"
                        placeholder="Ex: Pesto Pasta"
                        maxLength="50"
                        onChange={(event) => {props.setFoodName(event.target.value)}}
                        required
                    />
                </div>
                <br />
                <div className="form-group">
                    <label htmlFor="vegetarian"> Is this dish Vegetarian?</label>
                    <select
                        name="vegetarian"
                        onChange={(event) => {props.setVegetarian(event.target.value)}}
                    >
                        <option value="false">No</option>
                        <option value="true">Yes</option>
                    </select>
                </div>
                <br />
                <div className="form-group">
                    <label htmlFor="price">Price range:</label>
                    <select
                        name="price"
                        onChange={(event) => {props.setPriceRange(event.target.value)}}
                    >
                        <option value="$">$</option>
                        <option value="$$">$$</option>
                        <option value="$$$">$$$</option>
                    </select>
                </div>
                <br />
            </form>
                <button 
                    type="submit"
                    className="dinner--btn" 
                    onClick={props.addToList}
                >
                    Add to list
                </button>
        </div>
    )
}

服務器端：index.js

const express = require("express") // Set up an express server
const mongoose = require("mongoose") // Import Mongoose library
const cors = require('cors') // Import CORS to communicate with frontend
const app = express() // Initializing our express server

const DinnerModel = require('./models/Dinner')

app.use(express.json()) // Setting up Middleware
app.use(cors())

// Connect to MongoDB
mongoose.connect(
    'mongodb srv://higherstates:<password>@crud.cvewg.mongodb.net/dinner_ideas?retryWrites=true&w=majority', 
    {
        useNewUrlParser: true,
    }
)

// Create:
app.post("/insert", async (req, res) => {
    const foodName = req.body.foodName
    const isVegetarian = req.body.isVegetarian
    const priceRange = req.body.priceRange

    const dinner = new DinnerModel(
        { 
            foodName: foodName, 
            isVegetarian: isVegetarian,
            priceRange: priceRange,
        }
    )

    try {
        await dinner.save()
        res.send("data inserted")
    } catch(err) {
        console.log(err)
    }
})

// Read:
app.get("/read", async (req, res) => {
    DinnerModel.find({}, (err, result) => {
        if (err) {
            res.send(err)
        }
        res.send(result)
    })
})

// Update:
app.put("/update", async (req, res) => {
    const newFoodName = req.body.newFoodName
    const id = req.body.id

    try {
        await DinnerModel.findById(id, (err, updatedFood) => {
            updatedFood.foodName = newFoodName
            updatedFood.save()
            res.send("update")
        }).clone()
    } catch(err) {
        console.log("The error is: "   err)
    }
})


app.delete("/delete/:id", async (req, res) => {
    const id = req.params.id

    await DinnerModel.findByIdAndRemove(id).exec()
    res.send("deleted")
})

// Creating a port:
app.listen(3001, () => {
    console.log("Server is up on: http://localhost:3001")
})

食物串列組件：

export default function FoodListComponent(props) {
return (
    <div className="food-list container">
        <h1 className="food-list--title">Food List</h1>
        <table>
        <thead>
            <tr>
                <th className="th--name">Name</th>
                <th className="th--vegetarian">Vegetarian</th>
                <th className="th--price">Price</th>
                <th className="th--edit">Edit</th>
                <th className="th--actions">Action</th>
            </tr>
        </thead>
        <tbody>
            {props.foodList.length > 0 && props.foodList.map((val, key) => {
                return (
                    <tr key={key}>
                        <td>{val.foodName}</td>
                        <td>
                            {val.isVegetarian ? <input type="checkbox" checked readOnly /> : <input type="checkbox" disabled="disabled" readOnly  />}
                        </td>
                        <td>{val.priceRange}</td>
                        <td>
                        <input
                            name="edit"
                            placeholder="New food name.."
                            size="15"
                            maxLength="50"
                            onChange={(event) => {props.setNewFoodName(event.target.value)}}
                        >
                        </input>
                        </td>
                        <td>
                            <button
                                className="table--btn"
                                onClick={() => props.updateFood(val._id)}
                            >
                                Update
                            </button>
                            <button 
                                className="table--btn"
                                onClick={() => props.deleteFood(val._id)}
                            >
                                ?
                            </button>
                        </td>
                    </tr>
                )
            })}
        </tbody>
        </table>
    </div>
  )
}

貓鼬架構：

    const mongoose = require('mongoose')
    
    const DinnerSchema = new mongoose.Schema({
        foodName: {
            type: String,
            default: true,
        },
        isVegetarian: {
            type: Boolean,
            required: true,
        },
        priceRange: {
            type: String,
            required: true,
        }
    })

const Dinner = mongoose.model("Dinner", DinnerSchema)
module.exports = Dinner

這是演示：

https://i.stack.imgur.com/cyAtQ.gif [Demonstrating gif]

2. The app crashed and here's the error message in the server's terminal

https://i.stack.imgur.com/bgayZ.jpg [nodemon app crashed error]

Thanks everyone!

uj5u.com熱心網友回復：

 // Update:
    const updateFood = (id) => {
if(newFoodName){
      Axios.put("http://localhost:3001/update", {
        id: id,
        newFoodName: newFoodName,
      })
      .catch(error => console.log(`Hey, the error is ${error}`))
    }
}

標籤：reactjs mongodb axios schema nodemon

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