morgan是express默认的日志中间件，通过插拔方式引入express框架中，本文将从以下几方面内容展开。

• 日志控制台显示

// 安装包
$npm install express morgan -s
var express = require('express');
var app = express();
var morgan = require('morgan');app.use(morgan('short'));
app.use(function(req, res, next){res.send('ok');
});app.listen(3000);$node basic.js
::ffff:127.0.0.1 - GET / HTTP/1.1 304 - - 3.019 ms
::ffff:127.0.0.1 - GET /favicon.ico HTTP/1.1 200 2 - 0.984 ms

• 日志文件保存

var accessLogStream = fs.createWriteStream(path.join(__dirname, 'access.log'), {flags: 'a'});
app.use(morgan('short', {stream: accessLogStream}));

• API介绍

morgan(format, options) 返回express的中间件
参数说明：
format：可选，morgan与定义了几种日志格式，每种格式都有对应的名称，比如combined、short等，默认是default
options：可选，配置项，包含stream（常用）、skip、immediate
stream：日志的输出流配置，默认是process.stdout
skip：是否跳过日志记录

morgan('combined', {skip: function (req, res) { return res.statusCode < 400 }
})

immediate：布尔值，默认是false。当为true时，一收到请求，就记录日志；如果为false，则在请求返回后，再记录日志

自定义fromt

var express = require('express');
var app = express();
var morgan = require('morgan');morgan.format('joke', '[joke] :method :url :status');app.use(morgan('joke'));app.use(function(req, res, next){res.send('ok');
});app.listen(3000);

自定义token

var express = require('express');
var app = express();
var morgan = require('morgan');// 自定义token
morgan.token('from', function(req, res){return req.query.from || '-';
});// 自定义format，其中包含自定义的token
morgan.format('joke', '[joke] :method :url :status :from');// 使用自定义的format
app.use(morgan('joke'));app.use(function(req, res, next){res.send('ok');
});app.listen(3000);

• 日志切割

var FileStreamRotator = require('file-stream-rotator')
var express = require('express')
var fs = require('fs')
var morgan = require('morgan')
var path = require('path')var app = express()
var logDirectory = path.join(__dirname, 'log')// ensure log directory exists
fs.existsSync(logDirectory) || fs.mkdirSync(logDirectory)// create a rotating write stream
var accessLogStream = FileStreamRotator.getStream({date_format: 'YYYYMMDD',filename: path.join(logDirectory, 'access-%DATE%.log'),frequency: 'daily',verbose: false
})// setup the logger
app.use(morgan('combined', {stream: accessLogStream}))app.get('/', function (req, res) {res.send('hello, world!')
})

• 日志数据库存储

待续