nodejs入门

1、模块（模块的导入导出）

导出：

新建./count.js文件，内容为:

const counter = function (n) {
  return `counter: ${n}`
}

const adder = function (a, b) {
  return `adder: a + b = ${a + b}`
}

const PI = 3.14

/**[第一种导出方式]:只能导出一个；导入方式参照app.js中的第一种导入方式 */
module.exports = counter

/**[第二种导出方式]：导出多个 */
module.exports.counter = counter
module.exports.adder = adder
module.exports.PI = PI

/**[第三种导出方式]：导出多个 */
module.exports = {
  counter,
  adder,
  PI
}

导入：

新建./app.js文件，内容为：
app.js：

/**[第1种导入方式] start*/
var counter = require('./count.js')
console.log( counter(1) ) //result: counter: 1
/**[第1种导入方式] end*/

/**[第2种导入方式] start*/
var count = require('./count.js')
console.log( count.counter(1) )     //result: counter: 1
console.log( count.adder(2, 3) )    //result: adder: a + b = 5
console.log( count.pi )             //result: 3.14
/**[第2种导入方式] end*/

/**[第3种导入方式] start*/
var { counter, adder, pi } = require('./count.js')
console.log( counter(1) )     //result: counter: 1
console.log( adder(2, 3) )    //result: adder: a + b = 5
console.log( pi )             //result: 3.14
/**[第3种导入方式] end*/

然后使用node执行：node ./app.js，就可以看到相应的结果。

总结:

1.导出单个文件：module.exports = counter，导入使用var counter = require('./count.js')。

2.导出多个文件A：module.exports.counter = counter;，导入使用var count = require('./count.js')；

3.导出多个文件B：module.exports = { counter };，导入使用var { counter } = require('./count.js')；

2、事件

事件监听和触发

在app.js中加入:

var events = require('events');

var myEmitter = new events.EventEmitter();

myEmitter.on('someEvent', function (message) {
  console.log(message)
})

myEmitter.emit('someEvent', 'the event was emitted')

实例

var events = require('events');
var util = require('util')

function Person (name) {
  this.name = name
}

util.inherits(Person, events.EventEmitter);

var zhang3 = new Person('zhang3')
var li4 = new Person('li4')
var wang5 = new Person('wang5')

var persons = [zhang3, li4, wang5]

persons.forEach(person => {
  person.on('speak', (message) => {
    console.log( person.name + ' said: ' + message )
  })
})

zhang3.emit('speak', 'hi');
li4.emit('speak', 'i want a curry')

3、读写文件（同步、异步）

同步操作

  // 读取
  var hello = fs.readFileSync('./hello.txt', 'utf8')
  console.log( hello )
  console.log(111)
  // 写入
  fs.writeFileSync('writeMe.txt', hello) //会创建一个./writeMe.txt文件，内容为：hello.txt

异步操作

  // 读取-写入
    fs.readFile('./hello.txt', 'utf8', function (err, data) {
      console.log( data )
      fs.writeFile('writeMe.txt', data, function () {
        console.log('写入成功')  //会创建一个./writeMe.txt文件，内容为：hello.txt
      })
    })
    console.log(111)

4、创建和删除目录

var fs = require('fs')

fs.mkdirSync('stuff')  //创建目录
fs.rmdirSync('stuff') //删除目录

实践

创建一个./stuff目录，并读取./hello.txt中的内容，将其存入新建的./stuff/hello.txt文件中。

fs.mkdir('stuff', function () {
  console.log('文件夹创建成功')
  fs.readFile('./hello.txt', function(err, data) {
    console.log('文件读取成功')
    if(!err) {
      fs.writeFile('./stuff/hello.txt', data, function () {
        console.log('文件创建成功')
      })
    } else {
      console.log( 'read file error' )
    }
  })
})

5、流和管道

优点：处理数据、提高性能

流读写文件

  var fs = require('fs')
  var stream = fs.createReadStream(__dirname + '/count.js', 'utf8')
  var stream2 = fs.createWriteStream(__dirname + '/write.js')
  var n = ''
  stream.on('data', function (chunk) {
      //chunk数据流块
    n += chunk
    stream2.write(chunk)
  })
  stream.on('end', function () {
    console.log( n )  //输出所有内容
  })

  // 写入内容
  var writeData = 'hello world';
  stream2.write(writeData, 'utf8');
  stream2.end();
  stream2.on('finish', function () {
    console.log('finished')
  })

  // 管道|拷贝内容
  stream.pipe(stream2)

6、web服务器part1介绍

const http = require('http')

var server = http.createServer(function (req, res) {
  res.writeHead(200, { 'Content-Type': 'text/plain' });

  /**[第一种方式] */
  res.write('Hello World')
  res.end();

  /**[第二种方式] */
  res.end('Hello World');
})

server.listen(3000)

7、web服务器part2响应JSON

const http = require('http')

var server = http.createServer(function (req, res) {
  res.writeHead(200, { 'Content-Type': 'application/json' });

  var obj = {
    name: 'david',
    age: 12,
    job: 'web'
  }

  res.end(JSON.stringify(obj));
})

server.listen(3000)

8、web服务器part3响应html页面

const http = require('http')
const fs = require('fs')
const path = __dirname + '/index.html'


var server = http.createServer(function (req, res) {
  res.writeHead(200, { 'Content-Type': 'text/html' });

  var htmlFile = fs.createReadStream(path, 'utf8')

  htmlFile.pipe(res)
})

server.listen(3000)

9、web服务器part5模块化代码

新建./server.js

const http = require('http')
const fs = require('fs')
const path = __dirname + '/index.html'

function startServer () {
  var server = http.createServer(function (req, res) {
    res.writeHead(200, { 'Content-Type': 'text/html' });
  
    var htmlFile = fs.createReadStream(path, 'utf8')
  
    htmlFile.pipe(res)
  })

  server.listen(3000)
}

exports.startServer = startServer

./app.js

var server = require('./server')

server.startServer()

10、web服务器part5路由

./app.js

var server = require('./server')

server.startServer()

./server.js

const http = require('http')
const fs = require('fs')


function startServer () {
  var onRequest = function (req, res) {
    if(req.url === '/' || req.url === '/home') {
      // 是 / or /home 返回index.html
      res.writeHead(200, { 'Content-Type': 'text/html' });
      const path = __dirname + '/index.html'
      fs.createReadStream(path, 'utf8').pipe(res)
    } else if (req.url === '/review') {
      // 是 /review review.html
      res.writeHead(200, { 'Content-Type': 'text/html' });
      const path = __dirname + '/review.html'
      fs.createReadStream(path, 'utf8').pipe(res)
    } else if (req.url === '/api/v1/records') {
      // 是/api/v1/records 返回json
      res.writeHead(200, { 'Content-Type': 'application/json' });
      const obj = {
        name: 'david',
        age: 12,
        job: 'web'
      }
      res.end(JSON.stringify(obj))
    } else {
      // 否则，返回404页面
      res.writeHead(200, { 'Content-Type': 'text/html' });
      const path = __dirname + '/404.html'
      fs.createReadStream(path, 'utf8').pipe(res)   
    }
  }

  var server = http.createServer(onRequest)

  server.listen(3000)
  console.log( 'Server started on localhost port 3000; http://localhost:3000' )
}

exports.startServer = startServer

11、web服务器part6重构路由代码

目录结构:

/----
    app.js
    server.js
    route.js
    handler.js
    index.html
    review.html
    404.html

app.js

var server = require('./server')
var route = require('./route')
var handler = require('./handler')

/**[路由和渲染函数的映射] */
const handle = {};
handle['/'] = handler.home
handle['/home'] = handler.home
handle['/review'] = handler.review
handle['/api/v1/records'] = handler.api_records

server.startServer(route, handle)

server.js

const http = require('http')

function startServer (route, handle) {
  var onRequest = function (request, response) {
    route(handle, request.url, response)
  }

  var server = http.createServer(onRequest)

  server.listen(3000)
  console.log( 'Server started on localhost port 3000; http://localhost:3000' )
}

exports.startServer = startServer

route.js

const fs = require('fs')

function route (handle, pathname, response) {
  const routeFn = handle[pathname]

  if(typeof routeFn === 'function') {
    routeFn(response)
  } else {
    response.writeHead(200, { 'Content-Type': 'text/html' });
    fs.createReadStream(__dirname + '/404.html', 'utf8').pipe(response)   
  }
}

module.exports = route

handler.js

const fs = require('fs')

function home (response) {
  response.writeHead(200, { 'Content-Type': 'text/html' });
  fs.createReadStream( __dirname + '/index.html', 'utf8').pipe(response)
}

function review(response) {
  response.writeHead(200, { 'Content-Type': 'text/html' });
  fs.createReadStream(__dirname + '/review.html', 'utf8').pipe(response)
}

function api_records(response) {
  response.writeHead(200, { 'Content-Type': 'application/json' });
  const obj = {
    name: 'david',
    age: 12,
    job: 'web'
  }
  response.end(JSON.stringify(obj))
}

module.exports = {
  home,
  review,
  api_records
}

目前路由功能的结构分离成功。

12、web服务器part7使用get或者post发请求送数据

在上一节的基础上进行修改
server.js

const http = require('http')
const url = require('url')
const querystring = require('querystring')

function startServer (route, handle) {
  var onRequest = function (request, response) {
    const urlParse = url.parse(request.url, true)
    let data = [];

    request.on('error', function (err) {
      console.log(err)
    }).on('data', function (chunk) {
      /**[第一种方法] */
      // data += chunk
      /**[第二种方法] */
      data.push(chunk)
    }).on('end', function () {
      if(request.method.toLocaleUpperCase() === 'POST') {
        data = Buffer.concat(data).toString();
        route(handle, urlParse.pathname, response, querystring.parse(data))    
      } else {
        route(handle, urlParse.pathname, response, urlParse.query)
      }
    })
  }

  var server = http.createServer(onRequest)

  server.listen(3000)
  console.log( 'Server started on localhost port 3000; http://localhost:3000' )
}

exports.startServer = startServer

route.js

const fs = require('fs')

function route (handle, pathname, response, params) {
  const routeFn = handle[pathname]

  if(typeof routeFn === 'function') {
    routeFn(response, params)
  } else {
    response.writeHead(200, { 'Content-Type': 'text/html' });
    fs.createReadStream(__dirname + '/404.html', 'utf8').pipe(response)   
  }
}

module.exports = route

handler.js

const fs = require('fs')

function home (response) {
  response.writeHead(200, { 'Content-Type': 'text/html' });
  fs.createReadStream( __dirname + '/index.html', 'utf8').pipe(response)
}

function review(response) {
  response.writeHead(200, { 'Content-Type': 'text/html' });
  fs.createReadStream(__dirname + '/review.html', 'utf8').pipe(response)
}

function api_records(response, params) {
  response.writeHead(200, { 'Content-Type': 'application/json' });
  response.end(JSON.stringify(params))
}

module.exports = {
  home,
  review,
  api_records
}

index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>nodejs</title>
</head>
<body>
  <h1>hello nodejs</h1>
  <form action="api/v1/records" method="POST">
    name: <input type="text" name="name">
    age: <input type="text" name="age">
    <input type="submit" value="提交">
  </form>
</body>
</html>

总结

1.模块的导入导出

2.事件的监听和触发

3.文件读写删

4.文件夹的增删

5.文件流的读取和写入

6.使用node搭建服务

7.web服务器返回JSON

8.web服务器返回html

9.web服务器代码模块化

10.添加路由

11.模块化路由代码

12.使用get、post接收发送数据