Node.js表单提交报错求助：TypeError读取conteudo属性失败

报错信息 #

TypeError: Cannot read properties of undefined (reading 'conteudo')

问题代码 #

const express=require("express");
const app=express();
const handlebars=require("express-handlebars");
const Sequelize=require("sequelize");


const sequelize=new Sequelize("test","root","88182231",{
    host:"localhost",
    dialect:"mysql"
})

app.get("/card",function(req,res){
    res.render("form")
})

app.post("/add",function(req,res){
     res.send("conteudo:"+req.body.conteudo+" titulo:"+req.body.titulo)
})

app.engine("handlebars", handlebars.engine({ defaultLayout: "main" }));
app.set("view engine","handlebars");
app.use(express.urlencoded({extended:false}))
app.use(express.json())

解决方案 #

问题根源是Express的请求体解析中间件被放在了路由定义之后，导致路由处理函数执行时req.body未被解析，处于undefined状态，因此无法读取conteudo属性。

只需将express.urlencoded和express.json中间件的调用移到所有路由定义之前即可修复：

const express=require("express");
const app=express();
const handlebars=require("express-handlebars");
const Sequelize=require("sequelize");

// 先加载请求体解析中间件
app.use(express.urlencoded({extended:false}))
app.use(express.json())

const sequelize=new Sequelize("test","root","88182231",{
    host:"localhost",
    dialect:"mysql"
})

app.get("/card",function(req,res){
    res.render("form")
})

app.post("/add",function(req,res){
     res.send("conteudo:"+req.body.conteudo+" titulo:"+req.body.titulo)
})

app.engine("handlebars", handlebars.engine({ defaultLayout: "main" }));
app.set("view engine","handlebars");

Express中间件按顺序执行，只有先通过解析中间件处理请求，后续路由才能访问到解析后的req.body。你之前更换数据库、修改数据类型的操作和该报错无关，因为问题出在请求体解析环节，尚未涉及数据库操作。

内容的提问来源于stack exchange，提问作者Luiz Fernando da silva