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 - 1console.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_callbackhttp.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 = 0function 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]))

NodeSchool之learnyounode