81.node.js前端html时页面格式错乱解决办法

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

http.createServer(function(req, res) {
    //得到用户的路径
    var pathname = url.parse(req.url).pathname;
    //默认首页
    if (pathname == "/") {
        pathname = "index.html";
    }
    //拓展名
    var extname = path.extname(pathname);

    //真的读取这个文件
    fs.readFile("./" + pathname, function(err, data) {
        if (err) {
            //如果此文件不存在，就应该用404返回
            fs.readFile("./static/404.html", function(err, data) {
                res.writeHead(404, {
                    "Content-type": "text/html;charset=UTF8"
                });
                res.end(data);
            });
            return;
        };
        //MIME类型，就是
        //网页文件：  text/html
        //jpg文件 :   image/jpg
        var mime = getMime(extname);
        res.writeHead(200, {
            "Content-type": mime
        });
        res.end(data);
    });

}).listen(3000, "127.0.0.1");

function getMime(extname) {
    switch (extname) {
        case ".html":
            return "text/html";
            break;
        case ".jpg":
            return "image/jpg";
            break;
        case ".css":
            return "text/css";
            break;
    }
}