- 创建应用的过程和应用本身要进行分离。
- 路由和创建应用的过程也做一个分离。
下面实现创建应用的过程和应用本身要进行分离：
express.js
const Application = require("./application");function createApplication() {// 通过类来实现分离操作return new Application();
}module.exports = createApplication;
每次创建一个应用，路由系统应该是毫无关系的，应该创建一个全新的路由系统
新建 application.js
const http = require("http");
const url = require("url");function Application() {this.routers = [{path: "*",method: "all",handler: (req, res) => {res.end(`kaimo-express Cannot ${req.method} ${req.url}`);}} // 默认路由];
}Application.prototype.get = function (path, handler) {this.routers.push({path,method: "get",handler});
};Application.prototype.listen = function () {const server = http.createServer((req, res) => {const { pathname } = url.parse(req.url);const requestMethod = req.method.toLowerCase();for (let i = 1; i < this.routers.length; i++) {let { path, method, handler } = this.routers[i];if (path === pathname && method === requestMethod) {return handler(req, res);}}return this.routers[0].handler(req, res);});server.listen(...arguments);
};module.exports = Application;
测试一下：
const express = require("./kaimo-express");
const app = express();// 调用回调时 会将原生的 req 和 res 传入（req，res 在内部也被扩展了）
// 内部不会将回调函数包装成 promise
app.get("/", (req, res) => {res.end("ok");
});app.get("/add", (req, res) => {res.end("add");
});app.listen(3000, () => {console.log(`server start 3000`);console.log(`在线访问地址：http://localhost:3000/`);
});
