A brief introduction to getting started with Node.js and Express (pictures and text)

node -v

node

var num1 = 10;
var num2 = 20;
console.log(num1 + num2);

{
 "name": "Node_Hello",
 "description": "nodejs hello world app",
 "version": "0.0.1",
 "private": true,
 "dependencies": {
  "express": "4.x"
 }
}

npm install

var express = require('express');
var app = express();
app.get('/', function (req, res) {
 res.send(&#39;<h1>你好，这是我们的第一个nodejs项目</h1>&#39;);
});
app.listen(8080);

//加载模块
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
//加载路由文件
var index = require('./routes/index');
var users = require('./routes/users');

// 生产一个express的实例
var app = express();

// view engine setup
/*
设置 views 文件夹为存放视图文件的目录,
即存放模板文件的地方,dirname 为全局变量,
存储当前正在执行的脚本所在的目录。
 */
app.set('views', path.join(dirname, 'views'));
//设置模板引擎为ejs
app.set('view engine', 'ejs');

// uncomment after placing your favicon in /public
//app.use(favicon(path.join(dirname, 'public', 'favicon.ico')));
//加载日志中间件
app.use(logger('dev'));
//加载解析json的中间件
app.use(bodyParser.json());
//加载解析urlencoded请求体的中间件。 post请求
app.use(bodyParser.urlencoded({extended: false}));
//加载解析cookie的中间件
app.use(cookieParser());
//设置public文件夹为放置静态文件的目录
app.use(express.static(path.join(dirname, 'public')));

// 路由控制器。
app.use('/', index); // http://localhost:3000
app.use('/users', users);  //http://localhost:3000/users


// catch 404 and forward to error handler
app.use(function (req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// 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');
});

//把app导出。 别的地方就可以通过 require("app") 获取到这个对象
module.exports = app;

#!/usr/bin/env node //表明是node可执行文件

/**
 * Module dependencies.
 */
//引入我们在app.js中导出的app模块
var app = require('../app');
//引入debuger模块，打印调试日志
var debug = require('debug')('hello:server');
//引入http模块
var http = require('http');

/**
 * Get port from environment and store in Express.
 */

var port = normalizePort(process.env.PORT || '3000');
app.set('port', port); //设置端口号

/**
 * Create HTTP server.
 */
//创建Http服务器
var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */
//监听指定的端口
server.listen(port);
//监听error事件。 onError是发生错误的时候的回调函数
server.on('error', onError);
//监听listening事件
server.on('listening', onListening);

/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
 var port = parseInt(val, 10);

 if (isNaN(port)) {
  // named pipe
  return val;
 }

 if (port >= 0) {
  // port number
  return port;
 }

 return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
 if (error.syscall !== 'listen') {
  throw error;
 }

 var bind = typeof port === 'string'
  ? 'Pipe ' + port
  : 'Port ' + port;

 // handle specific listen errors with friendly messages
 switch (error.code) {
  case 'EACCES':
   console.error(bind + ' requires elevated privileges');
   process.exit(1);
   break;
  case 'EADDRINUSE':
   console.error(bind + ' is already in use');
   process.exit(1);
   break;
  default:
   throw error;
 }
}
/**
 * Event listener for HTTP server "listening" event.
 */

function onListening() {
 var addr = server.address();
 var bind = typeof addr === 'string'
  ? 'pipe ' + addr
  : 'port ' + addr.port;
 debug('Listening on ' + bind);
}

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

/* GET home page. */
router.get('/', function(req, res, next) {
 res.render('index', { title: '育知同创' });
});

module.exports = router;
/*
 生成一个路由实例用来捕获访问主页的GET请求，
 导出这个路由并在app.js中通过app.use('/', routes);
 加载。这样，当访问主页时，就会调用res.render('index', { title: '育知同创' });
 渲染views/index.ejs模版并显示到浏览器中。
 */

//加载路由文件
var index = require('./routes/index'); //去掉
var users = require('./routes/users'); //去掉
// 路由控制器。
app.use('/', index); // http://localhost:3000 //去掉
app.use('/users', users);  //http://localhost:3000/users  //去掉

var routes = require('./routes/index');
routes(app);

module.exports = function (app) {
 //一个get请求的路由 http://localhost:3000
 app.get("/", function (req, res) {
   res.render("index", {title:"育知同创abc"})
 });
 //又一个请求路由：http://localhost:3000/abc
 app.get("/abc", function (req, res) {
   res.render("index", {title:"育知同创" + req.path})
 });
}

app.set('views', dirname + '/views');
app.set('view engine', 'ejs');

<!DOCTYPE html>
<html>
 <head>
  <title><%= title %></title>
  <link rel=&#39;stylesheet&#39; href=&#39;/stylesheets/style.css&#39; />
 </head>
 <body>
  <h1><%= title %></h1>
  <p>Welcome to <%- title %></p>
 </body>
</html>

router.get('/', function(req, res, next) {
 res.render(&#39;index&#39;, { title: "<a href=&#39;http://www.baidu.com&#39;>百度 </a>"});
});

// 则会用title的值去替换ejs中的相应的代码。

<!DOCTYPE html>
<html>
 <head>
  <title><a href=&#39;http://www.baidu.com&#39;>百度 </a></title>
  <link rel=&#39;stylesheet&#39; href=&#39;/stylesheets/style.css&#39; />
 </head>
 <body>
  <h1><a href=&#39;http://www.baidu.com&#39;>百度 </a></h1>
  <p>Welcome to <a href=&#39;http://www.baidu.com&#39;>百度 </a></p>
 </body>
</html>