express 框架实现

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

function createApp() {
  var app = {};
  var routes = [];

  // 将所有请求方式写入app对象中
  http.METHODS.forEach(method => {
    method = method.toLocaleLowerCase();
    app[method] = (path, handler) => {
      let route = {
        path,
        method,
        handler
      };
      routes.push(route);
    };
  });

  // 匹配剩余路由
  app.all = (path, handler) => {
    let route = {
      method: "all",
      path,
      handler
    };
    routes.push(route);
  };

  // 中间件
  app.use = (path, handler) => {
    if(handler === undefined) {
      handler = path;
      path = "/";
    }

    let route = {
      method: "middle",
      path,
      handler,
    }

    routes.push(route);
  }

  // 服务
  let server = http.createServer((req, res) => {
    let method = req.method.toLocaleLowerCase();
    let { pathname } = url.parse(req.url, true);
    pathname = decodeURI(pathname);
    // 循环路由，匹配到就执行它的handler函数
    // 用next函数
    let i = 0;

    let next = () => {
      if(i >= routes.length) return;
      let { method: m, path: p, handler: h } = routes[i];
      i++;
      if(m === 'middle') {
        // 匹配中间件
        if(p == '/' || p == pathname || pathname.startsWith(p+'/')) {
          h(req, res, next);
        } else {
          next();
        }
      } else {
        // 匹配一般路由
        if ((m == method || m == "all") && (p == pathname || p === "*")) {
          h(req, res);
        } else {
          next();
        }
      }
    }

    next();
  });

  app.listen = (...rest) => {
    server.listen(...rest);
  };

  return app;
}

module.exports = createApp;

静态资源服务中间价实现

const path = require("path");
const fs = require("fs");
const url = require('url');

const mime = {
  css: "text/css",
  gif: "image/gif",
  html: "text/html",
  ico: "image/x-icon",
  jpeg: "image/jpeg",
  jpg: "image/jpeg",
  js: "text/javascript",
  json: "application/json",
  pdf: "application/pdf",
  png: "image/png",
  svg: "image/svg+xml",
  swf: "application/x-shockwave-flash",
  tiff: "image/tiff",
  txt: "text/plain",
  wav: "audio/x-wav",
  wma: "audio/x-ms-wma",
  wmv: "video/x-ms-wmv",
  xml: "text/xml",
  unknown: "text/plain"
};

function static(basename) {
    return (req, res, next) => {
        let { pathname } = url.parse(req.url, true);
        pathname = decodeURI(pathname);
        let p = path.resolve(path.join(basename, pathname));
        fs.stat(p, (err, stats) => {
            if(err) next();
            if(stats && stats.isFile()) {
                let ext = path.extname(p).slice(1);
                res.writeHead(200, {"content-type": `${mime[ext]};charset=utf-8`})
                let rs = fs.createReadStream(p);
                rs.pipe(res);
            } else {
                next();
            }
        })
    }
}

module.exports = static;

使用

const createApp =  require('./app/index');
const static =  require('./app/static');

let app = createApp();

app.use(static('./static'));

app.all('*', (req, res) => {
    res.end('404');
});

app.listen(8080, '127.0.0.1');