原文：https://www.liaoxuefeng.com/wiki/1022910821149312/1099849448318080

url2-koa/
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+- .vscode/
|  |
|  +- launch.json <-- VSCode 配置文件
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+- controllers/
|  |
|  +- login.js <-- 处理login相关URL
|  |
|  +- users.js <-- 处理用户管理相关URL
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+- app.js <-- 使用koa的js
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+- package.json <-- 项目描述文件
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+- node_modules/ <-- npm安装的所有依赖包

controllers文件夹下处理业务的js文件

var fn_index = async (ctx, next) => {ctx.response.body = `<h1>Index</h1><form action="/signin" method="post"><p>Name: <input name="name" value="koa"></p><p>Password: <input name="password" type="password"></p><p><input type="submit" value="Submit"></p></form>`;
};var fn_signin = async (ctx, next) => {varname = ctx.request.body.name || '',password = ctx.request.body.password || '';console.log(`signin with name: ${name}, password: ${password}`);if (name === 'koa' && password === '12345') {ctx.response.body = `<h1>Welcome, ${name}!</h1>`;} else {ctx.response.body = `<h1>Login failed!</h1><p><a href="/">Try again</a></p>`;}
};module.exports = {'GET /': fn_index,'POST /signin': fn_signin
};

controllers文件夹下处理业务的js文件

var fn_hello = async (ctx, next) => {var name = ctx.params.name;ctx.response.body = `<h1>Hello, ${name}!</h1>`;
};module.exports = {'GET /hello/:name': fn_hello
};

将controllers文件夹下处理业务的文件加载到app.js中

var files = fs.readdirSync(__dirname + '/controllers');// 过滤出.js文件:
var js_files = files.filter((f)=>{return f.endsWith('.js'); // js_files是所有指定文件夹下js文件的集合
});// 处理每个js文件:
for (var f of js_files) {console.log(`process controller: ${f}...`);// 导入js文件:let mapping = require(__dirname + '/controllers/' + f); for (var url in mapping) {if (url.startsWith('GET ')) {// 如果url类似"GET xxx":var path = url.substring(4); // 去掉GETrouter.get(path, mapping[url]);console.log(`register URL mapping: GET ${path}`);} else if (url.startsWith('POST ')) {// 如果url类似"POST xxx":var path = url.substring(5);router.post(path, mapping[url]);console.log(`register URL mapping: POST ${path}`);} else {// 无效的URL:console.log(`invalid URL: ${url}`);}}
}

封装

function addMapping(router, mapping) { // 把业务绑定到router上for (var url in mapping) {if (url.startsWith('GET ')) { // 判断开头的字母var path = url.substring(4); // 把GET 截掉router.get(path, mapping[url]); // eg:router.get('/hello/:name',fn_hello)console.log(`register URL mapping: GET ${path}`);} else if (url.startsWith('POST ')) {var path = url.substring(5);router.post(path, mapping[url]);console.log(`register URL mapping: POST ${path}`);} else {console.log(`invalid URL: ${url}`);}}
}function addControllers(router) { // 引入controllers下的js文件var files = fs.readdirSync(__dirname + '/controllers');var js_files = files.filter((f) => {return f.endsWith('.js');});for (var f of js_files) {console.log(`process controller: ${f}...`);let mapping = require(__dirname + '/controllers/' + f);addMapping(router, mapping); // 将这些js文件中的业务一一绑定}
}addControllers(router);

把以上的内容封装成一个中间件

const fs = require('fs');function addMapping(router, mapping) {...
}function addControllers(router, dir) {...
}module.exports = function (dir) {let controllers_dir = dir || 'controllers', // 如果不传参数，扫描目录默认为'controllers'router = require('koa-router')();addControllers(router, controllers_dir); // router当前的路由对象,controllers_dir是存放处理业务js的地址return router.routes();
};

使用

const controller = require('./controller'); // 引入controller...// 使用middleware:
app.use(controller()); // 自动处理绑定router对象上的路由地址和处理业务