Question

尝试通过this tutorial学习Expresss.js，我正要添加路由。我相信我已经完全按照本教程进行了操作，但是出现了这个错误：

[nodemon] starting `node ./bin/www`
/Users/dariusgoore/development/express-locallibrary-tutorial/node_modules/express/lib/router/route.js:202
    throw new Error(msg);
    ^

Error: Route.get() requires a callback function but got a [object  Undefined]
    at Route.(anonymous function) [as get] (/Users/dariusgoore/development/express-locallibrary-tutorial/node_modules/express/lib/router/route.js:202:15)
    at Function.proto.(anonymous function) [as get] (/Users/dariusgoore/development/express-locallibrary-tutorial/node_modules/express/lib/router/index.js:510:19)
    at Object.<anonymous> (/Users/dariusgoore/development/express-locallibrary-tutorial/routes/catalog.js:86:8)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:22:18)
    at Object.<anonymous> (/Users/dariusgoore/development/express-locallibrary-tutorial/app.js:9:21)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)

[nodemon]应用程序崩溃-等待文件更改，然后再开始...

以下是相关文件：

routes / catalog.js

var express = require('express');
var router = express.Router();

// Require controller modules.
var book_controller = require('../controllers/bookController');
var author_controller = require('../controllers/authorController');
var genre_controller = require('../controllers/genreController');
var book_instance_controller = require('../controllers/bookinstanceController');

/// BOOK ROUTES ///

// GET catalog home page.
router.get('/', book_controller.index);

// GET request for creating a Book. NOTE This must come before routes that display Book (uses id).
router.get('/book/create', book_controller.book_create_get);

// POST request for creating Book.
router.post('/book/create', book_controller.book_create_post);

// GET request to delete Book.
router.get('/book/:id/delete', book_controller.book_delete_get);

// POST request to delete Book.
router.post('/book/:id/delete', book_controller.book_delete_post);

// GET request to update Book.
router.get('/book/:id/update', book_controller.book_update_get);

// POST request to update Book.
router.post('/book/:id/update', book_controller.book_update_post);

// GET request for one Book.
router.get('/book/:id', book_controller.book_detail);

// GET request for list of all Book items.
router.get('/books', book_controller.book_list);

/// AUTHOR ROUTES ///

// GET request for creating Author. NOTE This must come before route for id (i.e. display author).
router.get('/author/create', author_controller.author_create_get);

// POST request for creating Author.
router.post('/author/create', author_controller.author_create_post);

// GET request to delete Author.
router.get('/author/:id/delete', author_controller.author_delete_get);

// POST request to delete Author.
router.post('/author/:id/delete', author_controller.author_delete_post);

// GET request to update Author.
router.get('/author/:id/update', author_controller.author_update_get);

// POST request to update Author.
router.post('/author/:id/update', author_controller.author_update_post);

// GET request for one Author.
router.get('/author/:id', author_controller.author_detail);

// GET request for list of all Authors.
router.get('/authors', author_controller.author_list);

/// GENRE ROUTES ///

// GET request for creating a Genre. NOTE This must come before route that displays Genre (uses id).
router.get('/genre/create', genre_controller.genre_create_get);

//POST request for creating Genre.
router.post('/genre/create', genre_controller.genre_create_post);

// GET request to delete Genre.
router.get('/genre/:id/delete', genre_controller.genre_delete_get);

// POST request to delete Genre.
router.post('/genre/:id/delete', genre_controller.genre_delete_post);

// GET request to update Genre.
router.get('/genre/:id/update', genre_controller.genre_update_get);

// POST request to update Genre.
router.post('/genre/:id/update', genre_controller.genre_update_post);

// GET request for one Genre.
router.get('/genre/:id', genre_controller.genre_detail);

// GET request for list of all Genre.
router.get('/genres', genre_controller.genre_list);

/// BOOKINSTANCE ROUTES ///

// GET request for creating a BookInstance. NOTE This must come before route that displays BookInstance (uses id).
router.get('/bookinstance/create', book_instance_controller.bookinstance_create_get);

// POST request for creating BookInstance.
router.post('/bookinstance/create', book_instance_controller.bookinstance_create_post);

// GET request to delete BookInstance.
router.get('/bookinstance/:id/delete', book_instance_controller.bookinstance_delete_get);

// POST request to delete BookInstance.
router.post('/bookinstance/:id/delete', book_instance_controller.bookinstance_delete_post);

// GET request to update BookInstance.
router.get('/bookinstance/:id/update', book_instance_controller.bookinstance_update_get);

// POST request to update BookInstance.
router.post('/bookinstance/:id/update', book_instance_controller.bookinstance_update_post);

// GET request for one BookInstance.
router.get('/bookinstance/:id', book_instance_controller.bookinstance_detail);

// GET request for list of all BookInstance.
router.get('/bookinstances', book_instance_controller.bookinstance_list);

module.exports = router;

在app.js中：

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var catalogRouter = require('./routes/catalog');  //Import routes for "catalog" area of site

var app = express();

//Set up mongoose connection
var mongoose = require('mongoose');
var mongoDB = 'mongodb://dariusgoore:654321cg@ds145704.mlab.com:45704/local_library_dg';
mongoose.connect(mongoDB);
mongoose.Promise = global.Promise;
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'MongoDB connection error:'));

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/catalog', catalogRouter);  // Add catalog routes to middleware chain.

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;

通过排除过程（并在错误跟踪中引用），导致错误的路由是此路由：

 // GET request for one Genre.
    router.get('/genre/:id', genre_controller.genre_detail);

注释该路线可消除错误，但我不知道为什么。

Answer 1

弄清楚了。控制器的动作拼写不同。

上面的路由器行引用了genre_controller.genre_detail

而控制器导出了genre_details

在控制器中更改详细信息可以解决此问题。

Express js Route.get（）需要回调函数，但是得到了[object Undefined]

1 个答案: