koa 简单的路由示例

app.js

const Koa = require('koa');
const app = new Koa()

const Router = require("./router");
const router = new Router();

router.get('/',(context,next)=>{
  context.body = 'index Page'
})

router.get('/hello',(context,next)=>{
  context.body = 'Hello Page'
})

router.get('/404',(context,next)=>{
  context.body = 'Page not Found'
})

app.use(router.routes())

app.listen(3000)

router.js

class Router {
  constructor() {
    // 缓存路由规则
    this._routes = [];
  }
  // 设置Method为GET的路由规则
  get(url, handler) {
    this._routes.push({
      url: url,
      methods: "GET",
      handler
    });
  }
  // 返回路由处理中间件给Koa使用
  routes() {
    return async (ctx, next) => {
      // 返回当前请求的URL和Method
      const { method, url } = ctx;
      const matchedRouter = this._routes.find(
        r => r.methods === method && url === r.url
      );
      // 从缓存的规则中找出匹配的规则
      if (matchedRouter && matchedRouter.handler) {
        // 执行路由规则中的处理函数，响应请求
        await matchedRouter.handler(ctx, next);
      } else {
        await next();
      }
    };
  }
}

module.exports = Router;