node.js - Express validation login form, how to judge?

Question

Problem description: Use express session to implement a login page. When using app.post to process the form, the judgment statement

if(req.body.password!=user[req.body.user].password||!user[req.body.user])

Among them, json file content is:

{
  "baidu":{
    "password":"123",
    "name":"百度"
  }
}

There is a problem, the specific manifestation is:

1. The username and password are placed in a json file and processed in app.js. When testing, if the username and password are correct, then It runs normally; however, if the username and password are incorrect, it displays:

TypeError: Cannot read property 'password' of undefined

I checked the information and consulted on overflow but I didn’t get a definite answer.

Are there any experts in this field who can provide some solutions?

The following is the code of app.js:

var express = require('express');
var user = require('./user');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var multer = require('multer');
var session = require('express-session');
var path = require('path');
var app = express();

app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));
app.use(cookieParser());

app.use(session({
    secret: 'baiduApp',
    cookie: {maxAge: 60 * 1000 * 30},
    resave: true,
    saveUninitialized: false
}));

app.get('/', function (req, res) {
    if (req.session.sign) {
        console.log(req.session);
        res.render('sign', {session: req.session})
    } else {
        res.render('index', {title: 'index'})
    }
});
app.get('/out', function (req, res) {
    req.session.destroy();
    res.redirect('/');
});

app.post('/sign', function (req, res) {
    //登录的数据和user.json中的数据进行对比
    if (req.body.password != user[req.body.user].password || !user[req.body.user]) {
        res.end('sign failure');
    } else {
        req.session.sign = true;
        req.session.name = user[req.body.user].name;
        res.send('welecome <strong>' + req.session.name + '</strong>，<a href="/out">登出</a>');
    }
});
app.listen(80);

Answer 1

if (req.body.password != user[req.body.user].password || !user[req.body.user]) {

The judgment here is written backwards
It should be:

if (!user[req.body.user] || req.body.password != user[req.body.user].password) {

First you have to determine whether there is req.body.userthis attribute in json.

Answer 2

I found another solution to this problem:

You should first determine whether you have an account, otherwise you will get cannot read property password of undefinedError:

if(!user[req.body.user] || req.body.password != user[req.body.user].password)｛
   //错误处理
｝

Combined with the previous reverse thinking, both solutions can solve this problem well.