我正在尝试按照教程使用Express在Node.js中制作表单。我正在编写验证逻辑，如果表单应该显示错误消息 为空提交，但是它没有这样做，而是在第 33 行给了我这个错误，我不知道为什么：
Cannot read property 'profileimage' of undefined
我调试了它，但无法弄清楚是什么原因造成的。 我做错了什么，我该如何解决？
这是表单代码：
var express = require('express');
var router = express.Router();
/* GET users listing. */
router.get('/', function(req, res, next) {
res.send('respond with a resource');
});
router.get('/register', function(req, res, next) {
res.render('register', {
'title': 'Register'
});
});
router.get('/login', function(req, res, next) {
res.render('login', {
'title': 'Log In'
});
});
router.post('/register', function(req, res, next) {
var name = req.body.name;
var email = req.body.email;
var username = req.body.username;
var password = req.body.password;
var password2 = req.body.password2;
// Check for Image Field
if(req.files.profileimage){
console.log('uploading File...');
// File Info
var profileImageOriginalName = req.files.profileimage.originalname;
var profileImageName = req.files.profileimage.name;
var profileImageMime = req.files.profileimage.mimetype;
var profileImagePath = req.files.profileimage.path;
var profileImageExt = req.files.profileimage.extension;
var profileImageSize = req.files.profileimage.size;
} else {
// Set a Default Image
var profileImageName = 'noimage.png';
}
// Form Validation
req.checkBody('name','Name field is required').notEmpty();
req.checkBody('email','Email field is required').notEmpty();
req.checkBody('email','Email not valid').isEmail();
req.checkBody('username','Username field is required').notEmpty();
req.checkBody('password','Password field is required').notEmpty();
req.checkBody('password2','Password do not match').equals(req.body.password);
// Check for errors
var errors = req.validationErrors();
if(errors){
res.render('register', {
errors: errors,
name: name,
email: email,
username: username,
password: password,
password2: password2
});
} else {
var newUser = new User({
name: name,
email: email,
username: username,
password: password,
profileImage: profileImageName
});
// Create User
User.createUser(newUser, function(err, user){
if(err)throw err;
console.log(user);
});
//Success Message
req.flash('success', 'You are now registered and may log in');
res.location('/');
res.redirect('/');
}
});
module.exports = router;
和我的应用程序.js：
var express = require('express');
var path = require('path');
var logger = require('morgan');
var expressValidator = require('express-validator');
var cookieParser = require('cookie-parser');
var session = require('express-session');
var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var bodyParser = require('body-parser');
var multer = require('multer');
var flash = require('connect-flash');
var mongo = require('mongodb');
var mongoose = require('mongoose');
var db = mongoose.connection;
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
// Handle file uploads
var multer = require('multer');
var upload = multer({ dest: './uploads' });
// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
// Handle Express Sessions
app.use(session({
secret:'secret',
saveUninitialized: true,
resave: true
}));
// passport
app.use(passport.initialize());
app.use(passport.session());
// Validator
app.use(expressValidator({
errorFormatter: function(param, msg, value) {
var namespace = param.split('.')
, root = namespace.shift()
, formParam = root;
while(namespace.length) {
formParam += '[' + namespace.shift() + ']';
}
return {
param : formParam,
msg : msg,
value : value
};
}
}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use(flash());
app.use(function (req, res, next) {
res.locals.messages = require('express-messages')(req, res);
next();
});
app.get('*', function(req, res, next){
res.locals.user = req.user || null;
next();
});
app.use('/', routes);
app.use('/users', users);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
module.exports = app;
首先files应该是一个数组。如果您确定只发送一个文件，请尝试使用此代码块：
// Check for Image Field
if(req.files && req.files[0] && req.files[0].profileimage){
console.log('uploading File...');
// File Info
var profileImageOriginalName = req.files[0].profileimage.originalname;
var profileImageName = req.files[0].profileimage.name;
var profileImageMime = req.files[0].profileimage.mimetype;
var profileImagePath = req.files[0].profileimage.path;
var profileImageExt = req.files[0].profileimage.extension;
var profileImageSize = req.files[0].profileimage.size;
} else {
// Set a Default Image
var profileImageName = 'noimage.png';
}
代码中有以下行：
if(req.files.profileimage){
当files未定义时，这意味着req没有属性files(也许没有在此请求上发送文件？)，然后尝试访问其中的任何内容都会引发错误(如果您没有捕获它，则会使您的节点崩溃)
因此，首先您应该添加如下类型安全：
if(req.files && req.files.profileimage) {
或者，更严格，像这样：
if(typeof req.files === 'object' && req.files.profileimage) {
(注意：当且仅当代码的另一部分尚未保证它是安全的时，您应该进行类型安全测试，例如以前的类型安全测试，或者您在代码中明确分配了属性)
我还看到您正在使用 multer 在req对象中获取文件对象。根据其文档，files可以是数组，也可以是字符串到数组的对象，从"multer"npm 页面：
如果这样使用：
app.post('/photos/upload', upload.array('photos', 12), function (req, res, next) {
它将是一个数组：
req.files 是
photos文件的数组req.body 将包含文本字段(如果有)
或者，如果这样使用：
var cpUpload = upload.fields([{ name: 'avatar', maxCount: 1 }, { name: 'gallery', maxCount: 8 }])
app.post('/cool-profile', cpUpload, function (req, res, next) {
那么它将是一个(字符串 -> 数组)对象：
req.files 是一个对象(字符串 -> 数组)，其中字段名是键，值是文件数组
例如
req.files['avatar'][0] -> File
req.files['gallery'] -> Array
因此，您应该相应地更改代码。例如，如果选择第二种方法，则应更改为以下内容：
if(typeof req.files === 'object' && req.files.profileimage) {
req.files.profileimage.forEach((profileimage) => {
//do anything you previously did on req.files.profileimage, on profileimage
let profileImageMime = profileimage.mimetype;
//... more things and code...
})
}