var http=require("http"),fs=require(‘fs‘);var server=http.createServer(function(req,res){    if("GET"==req.method && "/images"==req.url.substr(0,7) && ".jpg"==req.url.substr(-4)){        fs.stat(__dirname+req.url,function(err,stat){//检测文件是否存在            if(err||!stat.isFile()){                res.writeHead(404);                res.end(‘NOT FOUND‘);                return;            }            serve(__dirname+req.url,"application/jpg");        });    }else if(‘GET‘==req.method && ‘/‘==req.url){        serve(__dirname+‘/index.html‘,‘text/html‘);    }else{        res.writeHead(404);        res.end("NOT FOUND");    }    function serve(path,type){        res.writeHead(200,{"Content-Type":"type"});        fs.createReadStream(path).pipe(res);//将文件系统流接到http响应流中    }});server.listen(3000);