您可以通过将路由器作为中间件附加到其他路由器上（带有或不带有）来嵌套路由器
params。
{mergeParams: true}如果params要从父路由器访问，则必须传递到子路由器。
mergeParams在Express
4.5.0中引入（2014年7月5日）
在此示例中，路线上的
itemRouter附加到
userRouter``/:userId/items
这将导致以下可能的路线：
GET /user->
hello user
GET /user/5->
hello user 5
GET /user/5/items->
hello items from user 5
GET /user/5/items/6->
hello item 6 from user 5
var express = require('express');var app = express();var userRouter = express.Router();// you need to set mergeParams: true on the router,// if you want to access params from the parent routervar itemRouter = express.Router({mergeParams: true});// you can nest routers by attaching them as middleware:userRouter.use('/:userId/items', itemRouter);userRouter.route('/') .get(function (req, res) { res.status(200) .send('hello users'); });userRouter.route('/:userId') .get(function (req, res) { res.status(200) .send('hello user ' + req.params.userId); });itemRouter.route('/') .get(function (req, res) { res.status(200) .send('hello items from user ' + req.params.userId); });itemRouter.route('/:itemId') .get(function (req, res) { res.status(200) .send('hello item ' + req.params.itemId + ' from user ' + req.params.userId); });app.use('/user', userRouter);app.listen(3003);
