Nodejs in Visual Studio Code 02.学习Nodejs

1.开始

源码下载：https://github.com/sayar/NodeMVA

在线视频：https://mva.microsoft.com/en-US/training-courses/using-node-js-with-visual-studio-code-13920

2.事件驱动编程语言Nodejs

阻塞与非阻塞(Blocking I/O and Non Blocking I/O)

Blocking I/O

var fs = require('fs');

var contents = fs.readFileSync('package.json').toString();
console.log(contents);

Non Blocking I/O

var fs = require('fs');

fs.readFile('package.json', function (err, buf) {
     console.log(buf.toString());
});

Nodejs与C#相反，readFileSync表示阻塞线程，而readFile不阻塞线程异步执行方法，调用完成后执行callback方法。

注：在c#中同步方法一般为object.action，同步方法会阻塞线程等待耗时操作执行完成，异步方法为object.actionAsyc，异步方法经常有个异步事件可以注册待异步方法执行结束后调用。

3.Hello World

打开源码文件夹01_HelloWorld，包含两个文件app.js和package.json

app.js

console.log('Hello world'); //在控制台中输出Hello World ， 令人熟悉的console类

package.json

{
  "name": "_01_HelloWorld",
  "version": "0.0.0",
  "description": "Hello World",
  "main": "app.js",
  "author": {
    "name": "Rami Sayar",
    "email": ""
  }
}

打开CMD执行命令node app可以看到执行结果Hello World。

$ cd 01_HelloWorld
$ node app
Hello World

　　

4.FileIO

打开源码文件夹03_FILEIO

app.js

var fs = require('fs');

//阻塞I/O toString 用起来很顺手，比学C#简单多了
var contents = fs.readFileSync('package.json').toString();
console.log(contents);

//非阻塞I/O
fs.readFile('package.json', function (err, buf) {
    console.log(buf.toString());
});

　　

5.Streams

打开源码文件夹06_Streams

app.js

var fs = require("fs");

// Read File
fs.createReadStream("package.json")
    // Write File
    .pipe(fs.createWriteStream("out-package.json"));

6.HelloWorldHttp

打开源码文件夹02_HelloWorldHttp

app.js

var http = require('http');

//处理http请求，返回200ok hello world
var server = http.createServer(function (request, response) {
    response.writeHead(200, { "Content-Type": "text/plain" });
    response.end("Hello World
");
});

//侦听7000端口
server.listen(7000);

7.HelloWorldTCP

打开源码文件夹05_HelloWorldTCP

server.js

var net = require('net');

// The handler argument is automatically set as a listener for the 'connection' event
var server = net.createServer(function (socket) {
    console.log("Connection from " + socket.remoteAddress);
    socket.end("Hello World
");
});

server.listen(7000, "127.0.0.1");

client.js

var net = require('net');

var client = new net.Socket();

client.connect(7000, "127.0.0.1");

client.on('data', function (data) {
    console.log('Data: ' + data);
    client.destroy();
});

// Add a 'close' event handler for the client socket
client.on('close', function () {
    console.log('Connection closed');
});

打开两个CMD窗口，这两个窗口将会互相通讯。

$ cd 05_HelloWorldTCP
$ node server

　　

$ cd 05_HelloWorldTCP
$ node client

8.Requests

打开源码文件夹10_Requests

app.js

var request = require("request");
 
request("http://www.bing.com", function(error, response, body) {
  console.log(body);
});