理解如何正确使用连接闪存与Express 4.x？
所以基本的是，我有一个login表单 – 如果用户input错误的帐户信息，我希望它重新回到login页面，并显示一条消息，说明他们input了错误的信息 – 现在，米只是试图在testing消息输出，以确保我有这个工作的理解。
我对于理解连接闪存的基本指南（因为这似乎是我需要的工具）有一个基本的指导，但我并不完全理解它 – 我写了一些代码来尝试实现它，但编译我的Jade文件时，我不断收到这个错误：
TypeError: index.jade:28 26| form.form-signin(method="post", action="/loginSuccess") 27| h2.form-signin-heading(style="text-align:center;") Please sign in > 28| if loginError.length > 0 29| p <strong>ERROR!</strong> #{ loginError } 30| label.sr-only(for="inputID") Student ID 31| input#inputID.form-control(type="text", name="userID", placeholder="User ID", required="", autofocus="") Cannot read property 'length' of undefined at eval (eval at <anonymous> (C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\lib\index.js:218:8), <anonymous>:11 4:16) at eval (eval at <anonymous> (C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\lib\index.js:218:8), <anonymous>:19 5:22) at res (C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\lib\index.js:219:38) at renderFile (C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\bin\jade.js:270:40) at C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\bin\jade.js:136:5 at Array.forEach (native) at Object.<anonymous> (C:\Users\Tai\AppData\Roaming\npm\node_modules\jade\bin\jade.js:135:9) at Module._compile (module.js:435:26) at Object.Module._extensions..js (module.js:442:10) at Module.load (module.js:356:32) 我的代码如下，我将不胜感激任何帮助，但如果有人能解释我做错了什么（或者至less链接到了解如何使用连接闪存）
app.js
var express = require('express'); var path = require('path'); var favicon = require('serve-favicon'); var logger = require('morgan'); var mongojs = require('mongojs'); var db = mongojs('advisingApp', ['advisingApp']); var session = require('express-session'); var cookieParser = require('cookie-parser'); var bodyParser = require('body-parser'); var routes = require('./routes/index'); var users = require('./routes/users'); var flash = require('connect-flash'); var app = express(); // view engine setup app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade'); // 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 })); app.use(cookieParser('secretString')); app.use( session({ secret: 'secretKeyCookie', resave: true, saveUninitialized: true }) ); app.use(flash()); app.use(express.static(path.join(__dirname, 'public'))); app.use('/', routes); app.use('/users', users); //All custom codes go after this comment line app.use(function (req, res) { // flash a message req.flash('info', 'hello!'); next(); }) app.all('/test', function(req, res){ res.send(JSON.stringify(req.flash('test'))); }); app.post("/loginSuccess", function (req, res) { console.log("POST Request Received"); console.log(req.body.userID); console.log(req.body.userPIN); db.advisingApp.find({ 'studentID': req.body.userID,'PIN': parseInt(req.body.userPIN) }, function(err, docs) { if(err) { console.log(err); return err; } else if(!docs || docs.length == 0) { console.log("User was not found!"); var msg = "Your username and/or password was incorrect. Please try again."; res.error(msg); res.render("/", { loginError : req.flash('info')}); } else { console.log(docs); res.render("home"); } //res.send(docs); }); }); // 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;
玉
doctype html html(lang="en") head meta(charset="utf-8") meta(http-equiv="X-UA-Compatible", content="IE=edge") meta(name="viewport", content="width=device-width, initial-scale=1") // The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags meta(name="description", content="") meta(name="author", content="") link(rel="icon", href="favicon.ico") title Signin Template for Bootstrap // Bootstrap core CSS link(href="/stylesheets/bootstrap.min.css", rel="stylesheet") // Custom styles for this template link(href="/stylesheets/style.css", rel="stylesheet") // Just for debugging purposes. Don't actually copy these 2 lines! //if lt IE 9 script(src="/javascripts/ie8-responsive-file-warning.js") // <script src="/javascripts/ie-emulation-modes-warning.js"></script> // HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries //if lt IE 9 script(src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js") script(src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js") body .container form.form-signin(method="post", action="/loginSuccess") h2.form-signin-heading(style="text-align:center;") Please sign in if loginError.length > 0 p <strong>ERROR!</strong> #{ loginError } label.sr-only(for="inputID") Student ID input#inputID.form-control(type="text", name="userID", placeholder="User ID", required="", autofocus="") label.sr-only(for="inputPIN") PIN: input#inputPIN.form-control(type="password", name="userPIN", placeholder="Password", required="") button.btn.btn-lg.btn-primary.btn-block(type="submit") Sign in // /container // IE10 viewport hack for Surface/desktop Windows 8 bug script(src="/javascripts/ie10-viewport-bug-workaround.js") //AngularJS CDN script(src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.7/angular.min.js")
你的代码有几个错误。 在继续之前，请通过快速指南路由 ， 编写中间件和使用中间件 。
您错过了中间件function中的next参数。 而且添加flash消息的中间件应该放在使用路由器的前面。 （我不知道路由器处理什么资源。）
app.use(function (req, res, next) { req.flash('info', 'hello!'); next(); }) app.use('/', routes); app.use('/users', users);
我怀疑这个中间件没有被调用，因为上面的代码错误，所以这个flash消息从来没有被设置。
当呈现响应时，如果Flash消息不存在，则loginError将不确定。 这就是你得到错误的原因Cannot read property 'length' of undefined 。
res.render("/", { loginError : req.flash('info')});
所以在玉石模板中，你应该像这样testingloginError ：
if loginError p <strong>ERROR!</strong> #{ loginError }