无法从命令行在 Node 上安装车把

Question

我一直在尝试让车把与节点一起使用。我的书指示我安装这样的车把：npm install --save express3-handlebar。这引发了错误

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

所以我尝试了npm install --save express-handlebar。

当我尝试启动服务器node meadowlark.js时，命令提示符显示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)

然后我注意到在我的索引文件中我仍然有

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');

所以我将其更改为从第三行中删除 3。仍然是同样长的错误行。我做错了什么来收到这个错误？安装车把时我不在正确的目录中吗？我已经从我的应用根目录中尝试过了，其中包含我的index.js的文件

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 Web Development with Node & Express（Ethan Brown）。

Answer 1

我在您的代码中看到的主要问题是您正在创建 app 的两个实例：

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

这意味着您在错误的应用实例上配置了把手，因此是 "No default engine was specified"。

如果您删除第二个实例，您应该是黄金。这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.');
});

您可以尝试在 require 语句中使用或不使用 3，但它应该可以工作。

希望对你有帮助！！！