初涉Node.js

Node.js的是建立在Chrome的JavaScript的运行时，可方便地构建快速，可扩展的网络应用程序的平台。

Node.js使用事件驱动、非阻塞I/ O模型，是轻量级、高效、完美的跨分布式设备运行数据密集型实时应用。

1、安装Node.js：http://www.nodejs.org/

测试安装正确性：安装之后会有一个命令行工具。打开命令行工具，然后输入node helloworld.js。

helloworld.js中只需简单的一句话：console.log("Hello World！");

2、构建应用的模块——一个基础的HTTP服务器（server.js）

在主要脚本（index.js）里引用http服务器模块并启动。

var
server = require("./server");
server.start();

测试：在命令行输入“node
index.js”，然后打开浏览器访问：http://localhost:8888/ ，网页显示“Hello
World!”。

这样我们就可以定义不同的模块分别放在不同的文件里了。

3、构建路由选择模块（router.js）

4、加入请求处理程序模块（requestHandlers.js）

下面以上传文件为例，展现各个模块间的关系。

server.js

var http
= require("http");
var url = require("url");

function start(route, handle)
{
function onRequest(request, response) {

var pathname =
url.parse(request.url).pathname;

console.log("Request
for " + pathname + " received.");

route(handle, pathname, response,
request);
}

http.createServer(onRequest).listen(8888);
console.log("Server has started.");
}
exports.start = start;

router.js

function
route(handle, pathname, response, request) {
console.log("About
to route a request for " + pathname);

if (typeof
handle[pathname] === 'function')
{
        handle[pathname](response,
request);
    }
else {
        console.log("No
request handler found for " + pathname);
        response.writeHead(404,
{ "Content-Type": "text/plain" });
        response.write("404
Not found");
        response.end();

}

exports.route = route;

requestHandler.js

var querystring =
require("querystring");
var fs = require("fs");
var formidable =
require("formidable");

var sys = require("sys");

function start(response, postData)
{
    console.log("Request
handler 'start' was called.");
    var
body = '<html>'
+
    '
< head>'
+
    '
< meta
http-equiv="Content-Type" content="text/html; ' +
    'charset=UTF-8"
/>' +
    '
< /head>'
+
    '
< body>'
+
    '
< form
action="/upload" enctype="multipart/form-data" ' +
    'method="post">'
+
    '
< input
type="file" name="upload" multiple="multiple" />' +
    '
< input
type="submit" value="Upload file" />' +
    '
< /form>'
+
    '
< /body>'
+
    '
< /html>';

response.writeHead(200,
{ "Content-Type": "text/html" });
response.write(body);

response.end();

}
function upload(response, request)
{
console.log("Request
handler 'upload' was called.");

var
form = new
formidable.IncomingForm();

form.uploadDir
= "temp";

console.log("about
to parse");

form.parse(request,
function (error, fields, files)
{
        console.log("parsing
done");
        //sys.puts(sys.inspect(files.upload,
true, null));
        fs.renameSync(files.upload.path,
"./temp/test.jpg");
        response.writeHead(200,
{ "Content-Type": "text/html" });
        response.write("received
image: < br/>");

response.write("
< img
src='/show' />");
response.end();

});

}

function show(response) {
    console.log("Request
handler 'show' was called.");
    fs.readFile("./temp/test.jpg",
"binary", function (error, file) {
        if
(error) {
            response.writeHead(500,
{ "Content-Type": "text/plain" });
            response.write(error
+ "\n");
            response.end();

}
else {
            response.writeHead(200,
{ "Content-Type": "image/jpeg" });
            response.write(file,
"binary");
            response.end();

}

});

}

exports.start = start;
exports.upload = upload;
exports.show = show;

index.js

var server = require("./server");
var router = require("./router");
var requestHandlers =
require("./requestHandlers");

var handle = {};
handle[/"] =
requestHandlers.start;
handle[/start"] =
requestHandlers.start;
handle[/upload"] =
requestHandlers.upload;
handle[/show"] =
requestHandlers.show;

server.start(router.route, handle);

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