NodeSchool之learnyounode

learnyounode是NodeSchool里介绍基本异步编程的课程，通过13个简单的练习可以学习异步io，http等知识。运行此课程使用如下命令

npm install -g learnyounode  #安装

learnyounode 运行

为方便以后复习，现将每一个练习的代码整理如下

hello_world（你好，世界）

 

console.log("HELLO WORLD")

baby_steps（婴儿学步）

 

//此例子演示从命令行接受参数的方法var result = 0

//process.argv[0]是node，process.argv[1]是脚本文件名，所以从2开始才是输入参数

for (var i = 2; i < process.argv.length; i++)

  result += Number(process.argv[i])



console.log(result)

my_first_io（第一个 I/O）

var fs = require('fs')



//使用同步的方式读取文件，返回值是一个Buffer对象

var contents = fs.readFileSync(process.argv[2])

var lines = contents.toString().split('\n').length - 1

console.log(lines)

my_first_async_io（第一个异步 I/O）

 

var fs = require('fs')

var file = process.argv[2]



fs.readFile(file, function (err, contents) {

  // fs.readFile(file, 'utf8', callback) can also be used

  var lines = contents.toString().split('\n').length - 1

  console.log(lines)

})

 

filtered_ls（LS 过滤器）

 

var fs = require('fs')

var path = require('path')

//异步的方式读取目录文件，详情http://nodejs.org/api/fs.html#fs_fs_readdir_path_callback

fs.readdir(process.argv[2], function (err, list) {

  list.forEach(function (file) {

    if (path.extname(file) === '.' + process.argv[3])

      console.log(file)

  })

})

 

make_it_modular（使其模块化）

solution.js

var filterFn = require('./solution_filter.js')

var dir = process.argv[2]

var filterStr = process.argv[3]



filterFn(dir, filterStr, function (err, list) {

  if (err)

    return console.error('There was an error:', err)



  list.forEach(function (file) {

    console.log(file)

  })

})

solution_filter.js

var fs = require('fs')

var path = require('path')



module.exports = function (dir, filterStr, callback) {



  fs.readdir(dir, function (err, list) {

    if (err)

      return callback(err)



    list = list.filter(function (file) {

      return path.extname(file) === '.' + filterStr

    })



    callback(null, list)

  })

}

 

http_client（HTTP 客户端）

 

var http = require('http')

//http://nodejs.org/api/http.html#http_http_get_options_callback

http.get(process.argv[2], function (response) {

  response.setEncoding('utf8')

  response.on('data', console.log)

  response.on('error', console.error)

})

 

http_collect（HTTP 收集器）

 

//运行此例子需要安装bl

// npm install bl

var http = require('http')

var bl = require('bl')



http.get(process.argv[2], function (response) {

  response.pipe(bl(function (err, data) {

    if (err)

      return console.error(err)

    data = data.toString()

    console.log(data.length)

    console.log(data)

  }))  

})

 

juggling_async（玩转异步）

 

var http = require('http')

var bl = require('bl')

var results = []

var count = 0



function printResults () {

  for (var i = 0; i < 3; i++)

    console.log(results[i])

}



function httpGet (index) {

  http.get(process.argv[2 + index], function (response) {

    response.pipe(bl(function (err, data) {

      if (err)

        return console.error(err)



      results[index] = data.toString()

      count++



      if (count == 3)

        printResults()

    }))

  })

}



for (var i = 0; i < 3; i++)

  httpGet(i)

 

time_server（授时服务器）

 

var net = require('net')



function zeroFill(i) {

  return (i < 10 ? '0' : '') + i

}



function now () {

  var d = new Date()

  return d.getFullYear() + '-'

    + zeroFill(d.getMonth() + 1) + '-'

    + zeroFill(d.getDate()) + ' '

    + zeroFill(d.getHours()) + ':'

    + zeroFill(d.getMinutes())

}



var server = net.createServer(function (socket) {

  socket.end(now() + '\n')

})



server.listen(Number(process.argv[2]))

 

http_file_server（HTTP 文件服务器）

 

var http = require('http')

var fs = require('fs')



var server = http.createServer(function (req, res) {

  res.writeHead(200, { 'content-type': 'text/plain' })



  fs.createReadStream(process.argv[3]).pipe(res)

})



server.listen(Number(process.argv[2]))

 

HTTP 大写转换器（HTTP 大写转换器）

 

var http = require('http')

var map = require('through2-map')



var server = http.createServer(function (req, res) {

  if (req.method != 'POST')

    return res.end('send me a POST\n')



  req.pipe(map(function (chunk) {

    return chunk.toString().toUpperCase()

  })).pipe(res)

})



server.listen(Number(process.argv[2]))

 

http_json_api_server（HTTP JSON API 服务器）

var http = require('http')

var url = require('url')



function parsetime (time) {

  return {

    hour: time.getHours(),

    minute: time.getMinutes(),

    second: time.getSeconds()

  }

}



function unixtime (time) {

  return { unixtime : time.getTime() }

}



var server = http.createServer(function (req, res) {

  var parsedUrl = url.parse(req.url, true)

  var time = new Date(parsedUrl.query.iso)

  var result



  if (/^\/api\/parsetime/.test(req.url))

    result = parsetime(time)

  else if (/^\/api\/unixtime/.test(req.url))

    result = unixtime(time)



  if (result) {

    res.writeHead(200, { 'Content-Type': 'application/json' })

    res.end(JSON.stringify(result))

  } else {

    res.writeHead(404)

    res.end()

  }

})

server.listen(Number(process.argv[2]))