javascript - TypeError : Cannot read property 'handle' of undefined --- if (fn. handle && fn.set) mount_app = fn

Question

请在这方面提供一些帮助，我将不胜感激。不确定这意味着什么，因为这是我第一次使用 node 和 express。我将 express 设置为与 Node 一起使用，并尝试遵循网站 Express.js 上的信息。请帮助理解我在这里可能遗漏的内容，将不胜感激。

...\node_modules\express\lib\application.js:178
if (fn.handle && fn.set) mount_app = fn;
^
TypeError: Cannot read property 'handle' of undefined
at Function.app.use (....\node_modules\express\lib\application.js:178:9)
at Object.<anonymous> (....\app.js:18:5)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:906:3


/**
 * Module dependencies.
 */
 var http = require('http'); 
//var express = require('../..');
var module = require("module")
var logger = require('morgan');
var express = require('express');
var app =  module.exports = express();
var silent = 'test' == process.env.NODE_ENV;
var httpServer = http.createServer(app);
var bodyParser = require('body-parser');
var methodOverride = require('method-override');
  // app middleware
app.use(express.static(__dirname + '/public'));
app.use(bodyParser());
app.use(methodOverride());
app.use(logErrors);
app.use(clientErrorHandler);
app.use(errorHandler); 
api.use(logger('dev'));
api.use(bodyParser());
/**
 * CORS support.
 */
api.all('*', function(req, res, next)
{
  if (!req.get('Origin')) return next();// use "*" here to accept any origin
  res.set('Access-Control-Allow-Origin', 'http://localhost:3000');
  res.set('Access-Control-Allow-Methods', 'GET, POST');
  res.set('Access-Control-Allow-Headers', 'X-Requested-With, Content-Type');
  res.set('Access-Control-Allow-Max-Age', 3600);
  if ('OPTIONS' == req.method) return res.send(200);
  next();
});
// middleware with an arity of 4 are considered error handling middleware. When you next(err)
// it will be passed through the defined middleware in order, but ONLY those with an arity of 4, ignoring regular middleware.
var clientErrorHandler=function(err, req, res, next) {
  if (req.xhr) {// whatever you want here, feel free to populate properties on `err` to treat it differently in here.
  res.send(err.status || 500, { error: err.message });
  } 
  else 
  { next(err);}
};
// create an error with .status. we can then use the property in our custom error handler (Connect repects this prop as well)
var error=function (status, msg) {
  var err = new Error(msg);
  err.status = status;
  return err;
};
var logErrors=function (err, req, res, next) {
  console.error(err.stack);
  next(err);
};
var errorHandler=function (err, req, res, next) {
  res.status(500);
  res.render('error', { error: err });
};
// general config
app.set('views', __dirname + '/views');
//app.set('view engine', 'jade');
// our custom "verbose errors" setting which we can use in the templates via settings['verbose errors']
app.enable('verbose errors');// disable them in production use $ NODE_ENV=production node examples/error-pages
if ('production' == app.settings.env) {app.disable('verbose errors');}
        silent || app.use(logger('dev'));
// Routes 
app.get('/404', function(req, res, next){
next();// trigger a 404 since no other middleware will match /404 after this one, and we're not responding here
});

app.get('/403', function(req, res, next){// trigger a 403 error
  var err = new Error('not allowed!');
  err.status = 403;
  next(err);
});

app.get('/500', function(req, res, next){// trigger a generic (500) error
  next(new Error('keyboard cat!'));
});

// Error handlers

// Since this is the last non-error-handling middleware use()d, we assume 404, as nothing else responded.
// $ curl http://localhost:3000/notfound
// $ curl http://localhost:3000/notfound -H "Accept: application/json"
// $ curl http://localhost:3000/notfound -H "Accept: text/plain"
app.use(function(req, res, next){
  res.status(404); 
  if (req.accepts('html')) {// respond with html page
    res.render('404', { url: req.url });
    return;
  } 
  if (req.accepts('json')) {// respond with json
    res.send({ error: 'Not found' });
    return;
  } 
  res.type('txt').send('Not found');// default to plain-text. send()
});

// error-handling middleware, take the same form as regular middleware, however they require an
// arity of 4, aka the signature (err, req, res, next).when connect has an error, it will invoke ONLY error-handling middleware.

// If we were to next() here any remaining non-error-handling middleware would then be executed, or if we next(err) to
// continue passing the error, only error-handling middleware would remain being executed, however here
// we simply respond with an error page.
app.use(function(err, req, res, next){
  // we may use properties of the error object here and next(err) appropriately, or if we possibly recovered from the error, simply next().
  res.status(err.status || 500);
  res.render('500', { error: err });
});

if (!module.parent) {// assigning to exports will not modify module, must use module.exports
  app.listen(3000);
  silent || console.log('Express started on port 3000');
};

Answer 1

问题是您正在尝试use() 一个尚 undefined variable 。如果您使用 function logErrors(err, req, res, next) { 语法而不是 var logErrors=function (err, req, res, next) {，您的 TypeErrors应该消失。