server.js 代码

var http = require("http");
var fs = require("fs");
var url = require("url");
var port = process.argv[2];

if (!port) {
  console.log("请指定端口号好不啦？\nnode server.js 8888 这样不会吗？");
  process.exit(1);
}

var server = http.createServer(function (request, response) {
  var parsedUrl = url.parse(request.url, true);
  var pathWithQuery = request.url;
  var queryString = "";
  if (pathWithQuery.indexOf("?") >= 0) {
    queryString = pathWithQuery.substring(pathWithQuery.indexOf("?"));
  }
  var path = parsedUrl.pathname;
  var query = parsedUrl.query;
  var method = request.method;

  /******** 从这里开始看，上面不要看 ************/

  console.log("有个傻子发请求过来啦！路径（带查询参数）为：" + pathWithQuery);

  response.statusCode = 200;
  //默认首页
  const filePath = path === "/" ? "/index.html" : path;
  const index = filePath.lastIndexOf(".");
  //suffix是后缀
  const suffix = filePath.substring(index);
  const fileTypes = {
    ".html": "text/html",
    ".css": "text/css",
    ".js": "text/javascript",
    ".png": "image/png",
    ".jpg": "image/jpeg",
  };
  response.setHeader(
    "Content-Type",
    `${fileTypes[suffix] || "text/html"};charset=utf-8`
  );
  let content;
  try {
    content = fs.readFileSync(`./public${filePath}`);
  } catch (error) {
    content = "文件不存在";
    response.statusCode = 404;
  }
  response.write(content);
  response.end();

  /******** 代码结束，下面不要看 ************/
});

server.listen(port);
console.log(
  "监听 " +
    port +
    " 成功\n请用在空中转体720度然后用电饭煲打开 http://localhost:" +
    port
);

注意：
const filePath = path === "/" ? "/index.html" : path; 的意思是申明文件的路径赋值于路径，路径等于/的话，默认的让filePath等于/index.html，如果不是，就是path。

let content;
  try {
    content = fs.readFileSync(`./public${filePath}`);
  } catch (error) {
    content = "文件不存在";
    response.statusCode = 404;
  }
  response.write(content);

意思是：try的意思是不确定会不会报错，catch是抓住的意思，申明一个content（内容），如果内容存在，则读取当前目录下的文件路径，否则抓住错误，内容为文件不存在，状态码404。

const index = filePath.lastIndexOf(".");
  //suffix是后缀
  const suffix = filePath.substring(index);
  const fileTypes = {
    ".html": "text/html",
    ".css": "text/css",
    ".js": "text/javascript",
    ".png": "image/png",
    ".jpg": "image/jpeg",
  };
  response.setHeader(
    "Content-Type",
    `${fileTypes[suffix] || "text/html"};charset=utf-8`
  );

意思：申明index是 . 的文件路径中的下标，申明后缀从.的下标开始获得子字符串，申明文件类型（hash表）有... 。${fileTypes[suffix] || "text/html"};charset=utf-8文件类型对应的后缀或HTML（兜底值）

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server.js 代码