let http = require('http');    let url = require('url');    let methods = require('methods');    let fs = require('fs');    // 主文件    function application() {      function app(req, res) {        let { pathname } = url.parse(req.url, true);        let requestMethod = req.method.toLowerCase();        let i = 0        function next(err) {          if (i === app.routes.length) return res.end(`Cannot ${requestMethod} ${pathname}`);          let layer = app.routes[i++];          let { path, method, callback } = layer; // 取出来的路径 可能是正则类型          if (err) { // 有没有错误 是不是错误处理中间件            if (method === 'middleware' && callback.length === 4) { // 是中间件              callback(err, req, res, next);            } else { // 如果有错误 把错误继续传递，找错误处理中间件              next(err);            }          } else {            if (method === 'middleware') {              // 中间件  /hello/  /hello/123123              // 是/  或者 路径相等 以中间件路径开头              if (path === '/' || path === pathname || pathname.startsWith(path + '/')) {                callback(req, res, next);              } else {                next();              }            } else {              if (path instanceof RegExp) { // 路径参数                if (path.test(pathname)) { // /article/([^\/]) /article/1                  let [, ...others] = pathname.match(path); // 匹配出来对用的路径参数                  req.params = path.params.reduce((memo, next, index) => (memo[next] = others[index], memo), {}); // 把两个数组合并成一个对象                  return callback(req, res);                } else {                  next();                }              } else {                if ((path == pathname || path == '*') && (method == requestMethod || method === 'all')) {                  callback(req, res);                } else {                  next();                }              }            }          }        }        next();      }      app.routes = []; // 路由的关系存放处            app.listen = function (...args) {        let server = http.createServer(app);        server.listen(...args);      };      // 中间件      app.use = function (path, callback) {        // 中间件第一个路径参数未传默认        if (typeof callback !== 'function') {          callback = path; // 没有传递路径 那么路径就是callback          path = '/' //路径默认为/ 全部匹配        }        let layer = {          path,          callback,          method: 'middleware' // 表示这个layer是一个中间件        }        app.routes.push(layer);      };          // 请求get、post...              [...methods, 'all'].forEach(method => {        app[method] = function (path, callback) {          // 路径参数              if (path.includes(':')) { // 是路径参数 /article/([^\/]*)            let params = []; // id            path = path.replace(/:([^\/]*)/g, function () {              params.push(arguments[1]);              return '([^\/]*)'            });            path = new RegExp(path);            path.params = params; // 把匹配到的数组 存在路径上          }          let layer = {            method,            path, // path如果是字符串我就认为是普通的路由            callback          }          app.routes.push(layer);        }      })          // 添加默认的一些请求和响应属性              app.use(function (req, res, next) {        let { query, pathname } = require('url').parse(req.url, true);        req.query = query;        req.path = pathname;        res.send = function (value) {          if (Buffer.isBuffer(value) || typeof value === 'string') {            res.end(value)          } else if (typeof value === 'object') {            res.setHeader('Content-Type', 'text/html;charset=utf8');            res.end(JSON.stringify(value))          }        }        next();      })      return app;    }    // 静态服务    application.static = function (dir) {      let path = require('path');      return function (req, res, next) {        let p = req.path;        let realPath = path.join(dir, p);        fs.stat(realPath, function (err, statObj) {          if (err) {            next();          } else {            if (statObj.isDirectory()) {                } else {              fs.readFile(realPath, 'utf8', function (err, data) {                if (err) {                  next();                }else{                  res.end(data);                }              })            }          }        })      }    }    module.exports = application;复制代码