87 # Separation of express applications and created applications

1. The process of creating an application should be separated from the application itself.
2. The process of routing and creating applications is also separated.

The following implements the separation of the process of creating an application from the application itself:

express.js

const Application = require("./application");

function createApplication() {
    
    
    // 通过类来实现分离操作
    return new Application();
}

module.exports = createApplication;

Every time you create an application, the routing system should be irrelevant and a completely new routing system should be created.

Newapplication.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;

have a test:

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/`);
});