Node.js 究竟是什么?

Node 是一个服务器端 JavaScript 解释器,它将改变服务器应该如何工作的概念。它的目标是帮助程序员构建高度可伸缩的应用程序,编写能够处理数万条同时连接到一个(只有一个)物理机的连接代码。


清单 2. Node 随机数字生成器
// these modules need to be imported in order to use them.
// Node has several modules. They are like any #include
// or import statement in other languages
var http = require(“http”);
var url = require(“url”);

// The most important line in any Node file. This function
// does the actual process of creating the server. Technically,
// Node tells the underlying operating system that whenever a
// connection is made, this particular callback function should be
// executed. Since we’re creating a web service with REST API,
// we want an HTTP server, which requires the http variable
// we created in the lines above.
// Finally, you can see that the callback method receives a ‘request’
// and ‘response’ object automatically. This should be familiar
// to any PHP or Java programmer.
http.createServer(function(request, response) {

// The response needs to handle all the headers, and the return codes
// These types of things are handled automatically in server programs
// like Apache and Tomcat, but Node requires everything to be done yourself
response.writeHead(200, {“Content-Type”: “text/plain”});

// Here is some unique-looking code. This is how Node retrives
// parameters passed in from client requests. The url module
// handles all these functions. The parse function
// deconstructs the URL, and places the query key-values in the
// query object. We can find the value for the “number” key
// by referencing it directly – the beauty of JavaScript.
var params = url.parse(request.url, true).query;
var input = params.number;

// These are the generic JavaScript methods that will create
// our random number that gets passed back to the caller
var numInput = new Number(input);
var numOutput = new Number(Math.random() * numInput).toFixed(0);

// Write the random number to response

// Node requires us to explicitly end this connection. This is because
// Node allows you to keep a connection open and pass data back and forth,
// though that advanced topic isn’t discussed in this article.

// When we create the server, we have to explicitly connect the HTTP server to
// a port. Standard HTTP port is 80, so we’ll connect it to that one.

// Output a String to the console once the server starts up, letting us know everything
// starts up correctly
console.log(“Random Number Generator Running…”);

将上面的代码放入一个名为 “random.js” 的文件中。现在,要启动这个应用程序并运行它(以便创建 HTTP 服务器并监听端口 80 上的连接),只需在您的命令提示中输入以下命令:% node random.js。下面是服务器已经启动并运行时看起来的样子:
root@ubuntu:/home/moila/ws/mike# node random.js
Random Number Generator Running…

应用程序已经启动并运行。Node 正在监听所有连接,我们来测试一下。由于我们创建了一个简单的 RESTful API,所以可以使用 Web 浏览器来访问这个应用程序。键入以下地址(确保您已完成了上面的步骤):http://localhost/?number=27。
您的浏览器窗口将更改到一个介于 0 到 27 之间的随机数字。单击浏览器上的 “重新载入” 按钮,您会得到另一个随机数字。就是这样,这就是您的第一个 Node 应用程序!




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