无法从命令行在节点上安装把手

Question

我一直试图让把手与节点一起使用.我的书已经指示我安装这样的把手:npm install --save express3-handlebar.这引发了一个错误

npm WARN deprecated express3-handlebars @0.5.2: THIS PACKAGE HAS BEEN RENAMED TO: express-handlebars

所以我试过了npm install --save express-handlebar.

当我尝试启动服务器时node meadowlark.js,显示命令提示符Express started on....

但是当我将localhost放入浏览器时,我收到以下信息:

Error: No default engine was specified and no extension was provided.
   at new View (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\view.js:48:42)
   at EventEmitter.app.render (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\application.js:509:12)
   at ServerResponse.res.render (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\response.js:904:7)
   at require.create.defaultLayout (C:\Users\myUserName\Desktop\project\meadowlark\site\meadowlark.js:20:6)
   at Layer.handle_error (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\layer.js:58:5)
   at trim_prefix (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\index.js:269:13)
   at C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\index.js:238:9
   at Function.proto.process_params (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\index.js:313:12)
   at C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\index.js:229:12
   at Function.match_layer (C:\Users\myUserName\Desktop\project\meadowlark\site\node_modules\express\lib\router\index.js:296:3)

然后我注意到我的索引文件中还有

var app = express();
// set up handlebars view engine
var handlebars = require('express3-handlebars')
    .create({ defaultLayout:'main' });
app.engine('handlebars', handlebars.engine);
app.set('view engine', 'handlebars');

所以我改变了,3从第三行删除.仍然是同样长的错误行.我收到此错误的错误是什么？当我安装把手时我不在正确的目录中吗？我已经从我的应用程序根目录中尝试了它,并且其中包含我的文件index.js

var express = require('express');
var app = express();
app.set('port', process.env.PORT || 3000);

app.get('/', function(req, res) {
 res.render('home');
});
app.get('/about', function(req, res) {
 res.render('about');
});
// 404 catch-all handler (middleware)
app.use(function(req, res, next){
 res.status(404);
 res.render('404');
});
// 500 error handler (middleware)
app.use(function(err, req, res, next){
 console.error(err.stack);
 res.status(500);
 res.render('500');
});

app.listen(app.get('port'), function() {
    console.log('Express started on http://localhost:' +
        app.get('port') + '; press Ctrl-C to terminate.');
});

var app = express();
// set up handlebars view engine
var handlebars = require('express3-handlebars')
    .create({ defaultLayout:'main' });
app.engine('handlebars', handlebars.engine);
app.set('view engine', 'handlebars');

我正在使用的示例来自使用Node&Express的Web开发(Ethan Brown).

Answer 1

我在您的代码中看到的主要问题是您正在创建两个实例app:

var app = express(); // I see this line twice in your code

这意味着您正在应用程序的错误实例上配置把手"No default engine was specified".

如果你删除第二个实例,你应该是金色的.以下是我将如何重写该代码的示例:

var express = require('express');
var app = express();
var handlebars = require('express-handlebars')
  .create({ defaultLayout:'main' });
app.engine('handlebars', handlebars.engine);
app.set('view engine', 'handlebars');

app.set('port', 3000);

app.get('/', function(req, res) {
  res.render('home');
});
app.get('/about', function(req, res) {
  res.render('about');
});
// 404 catch-all handler (middleware)
app.use(function(req, res, next){
  res.status(404);
  res.render('404');
});
// 500 error handler (middleware)
app.use(function(err, req, res, next){
  console.error(err.stack);
  res.status(500);
  res.render('500');
});

app.listen(app.get('port'), function() {
  console.log('Express started on http://localhost:' +
  app.get('port') + '; press Ctrl-C to terminate.');
});

您可以尝试使用和不使用3require语句,但它应该以任何方式工作.

希望这可以帮助!!!