目标

• 使用express实现一个监听3000端口的http服务如下

const express = require('express');
const app = express();app.get('/', (req, res) => {res.end('Hello Express');
})
app.get('/users',(req, res)=>{res.end(JSON.stringify({name: 'abc'}))
})
app.listen(3000, ()=>{console.log('[server] server is running at http://localhost:3000 ');
})

• 我们想将第一行代码变成如下的代码

const express = require('./lxpress.js');

• 即需要完成以下几个操作
  1.会有一个router数组,当使用app.get方法时,会将路径和回调函数传入
  2.调用listen方法时,会创建一个http服务.该服务会从router数组中取出所有的路由进行监听.然后根据传入的参数进行监听

实现

• /lxpress.js
• 基本架构

const http = require('http');
let routers = [];
class Application{get(){},listen(){}
}
module.exports = () =>{return new Application();
}

• get逻辑的实现.
  1.会接收2个参数,path和handler
  2.将参数推进routers中
  3.为了方便以后和POST方法区分,新增一个method属性

get(path, handler){routers.push({path,method:'GET',handler})
}

• listen逻辑的实现
  1.在里面会创建一个http服务,该服务接收request和response两个参数
  2.对routers里面的每一项进行解析,并为每一项指定路由处理函数handler
  3.接收的参数用…arguments展开执行

listen(){const server = http.createServer((req, res)=>{// 解构出pathname// 使用到了url的解析需要导入 url --> const url = require('url');const { pathname} = url.parse(req.url, true);for(let router of routers){const {path, method, handler} = router; // 从每一项路由中解构出path, method, handlerif(path === pathname && req.method === method){return handler(req, res);}}})server.listen(...arguments);	
}

总体代码如下:

• /lxpress.js

const http = require('http');
const url = require('url');const router = [];
class Application {get(path, handler) {router.push({path,method: 'get',handler})}listen() {const server = http.createServer((req, res) => {const { pathname } = url.parse(req.url, true);for (const item of router) {const { path, method, handler } = item;if (pathname === path && req.method.toLowerCase() === method) {return handler(req, res);}}})server.listen(...arguments);}
}module.exports = () => {return new Application()
}