http.createServerapp.listen 的区别是什么?

var express = require('express')
var app = express()
app.listen(3000)

var express = require('express')
var http = require('http')
var app = express()

http.createServer(app).listen(80)

两者都可以实现服务器监听,他们之间的区别是什么?

为了回答这个问题,需要阅读 express 的源文件

/**
 * Listen for connections.
 *
 * A node `http.Server` is returned, with this
 * application (which is a `Function`) as its
 * callback. If you wish to create both an HTTP
 * and HTTPS server you may do so with the "http"
 * and "https" modules as shown here:
 *
 *    var http = require('http')
 *      , https = require('https')
 *      , express = require('express')
 *      , app = express();
 *
 *    http.createServer(app).listen(80);
 *    https.createServer({ ... }, app).listen(443);
 *
 * @return {http.Server}
 * @public
 */

app.listen = function listen() {
  var server = http.createServer(this);
  return server.listen.apply(server, arguments);
};

可以看出,app.listen 其实是 http.createServer() 的简单封装,如果只是使用 http 服务器,app.listen() 就够用了。

但是如果你要监听 https 端口(或同时监听 http 80 端口和 https 443 端口),就要使用 https.createServer() 手动创建服务器,并将 express() 生成的应用当作参数传递进去。

REF