无法读取 FinalHandler 节点模块中未定义的属性“_header”

Question

我似乎无法找到解决我的问题的方法。我正在尝试启动我的 nodeJS/expressJS 应用程序，但在“npm start”时收到错误。

错误和堆栈跟踪：

    /Users/jmccreary/Documents/NewHireSite/node_modules/finalhandler/index.js:94
    if (!err && res._header) {
                   ^

TypeError: Cannot read property '_header' of undefined
    at /Users/jmccreary/Documents/NewHireSite/node_modules/finalhandler/index.js:94:20
    at /Users/jmccreary/Documents/NewHireSite/node_modules/express/lib/router/index.js:635:15
    at next (/Users/jmccreary/Documents/NewHireSite/node_modules/express/lib/router/index.js:210:14)
    at Function.handle (/Users/jmccreary/Documents/NewHireSite/node_modules/express/lib/router/index.js:174:3)
    at Function.handle (/Users/jmccreary/Documents/NewHireSite/node_modules/express/lib/application.js:174:10)
    at app (/Users/jmccreary/Documents/NewHireSite/node_modules/express/lib/express.js:38:9)
    at Object.<anonymous> (/Users/jmccreary/Documents/NewHireSite/app.js:101:25)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/Users/jmccreary/Documents/NewHireSite/bin/www:7:11)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:427:7)

违规代码（在node_modules/finalhandler/index.js中）：（
注意：我自己添加了console.logs，它们不是模块的一部分）

  function finalhandler (req, res, options) {
  var opts = options || {}
  console.log("The req is: ", req);
  console.log("The res is: ", res);

  // get environment
  var env = opts.env || process.env.NODE_ENV || 'development'

  // get error callback
  var onerror = opts.onerror

  return function (err) {
    var headers
    var msg
    var status

    // ignore 404 on in-flight response
    if (!err && res._header) {
      debug('cannot 404 after headers sent')
      return
    }
    ...

从我的 console.log() 来看，输出如下：

 The req is:  Authenticator {
  _key: 'passport',
  _strategies: { session: SessionStrategy { name: 'session' } },
  _serializers: [],
  _deserializers: [],
  _infoTransformers: [],
  _framework: 
   { initialize: [Function: initialize],
     authenticate: [Function: authenticate] },
  _userProperty: 'user',
  Authenticator: [Function: Authenticator],
  Passport: [Function: Authenticator],
  Strategy: { [Function: Strategy] Strategy: [Circular] },
  strategies: { SessionStrategy: { [Function: SessionStrategy] super_: [Object] } } }
 The res is:  undefined

编辑：我相信，这是调用错误的代码（来自node_modules/express/lib/application.js）：

 /**
 * Dispatch a req, res pair into the application. Starts pipeline processing.
 *
 * If no callback is provided, then default error handlers will respond
 * in the event of an error bubbling through the stack.
 *
 * @private
 */

app.handle = function handle(req, res, callback) {
  var router = this._router;

  // final handler
  var done = callback || finalhandler(req, res, {
    env: this.get('env'),
    onerror: logerror.bind(this)
  });

  // no routes
  if (!router) {
    debug('no routes defined on app');
    done();
    return;
  }

  router.handle(req, res, done);
};

我的package.json文件（使用Express 4）如下：

{
  "name": "newhiresite",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
"dependencies": {
    "body-parser": "~1.17.1",
    "connect-flash": "^0.1.1",
    "cookie-parser": "~1.4.3",
    "debug": "~2.6.3",
    "express": "~4.15.2",
    "express-session": "^1.15.3",
    "express-validator": "^3.2.0",
    "fs": "0.0.1-security",
    "mongodb": "^2.2.25",
    "mongoose": "^4.10.1",
    "morgan": "~1.8.1",
    "node-sass-middleware": "0.9.8",
    "passport": "~0.3.2",
    "passport-local": "~1.0.0",
    "pug": "~2.0.0-rc.1",
    "serve-favicon": "~2.4.2"
  }
}

我能够很好地运行教程的源代码，并且它具有与我的应用程序相同的模块，几乎相同（除了 npm start 命令上的 www/bin 文件）。我尝试删除其他模块并移动 app.js 文件中的内容，但无济于事。

任何指示或帮助将不胜感激。谢谢你！

Answer 1

我有同样的错误。以下内容为我解决了问题，也许也适合您？我有这个代码：

var express = require('express')();
var app = express();

app.listen(3000, function () {
  console.log('Example app listening at http://%s:%s');
});

它的 () 太多了。删除它解决了问题：

var express = require('express');