Express: why middlewares doesn't work properly for independent routers?-CodePudding

I have the following code with 3 independent routers

const Express = require("express")

const app = Express()

const usersRouter = Express.Router()
const productsRouter = Express.Router()
const storeRouter = Express.Router()

productsRouter.use((_, res, next) => {
  res.send("products fail")
  //next()
})

storeRouter.use((_, res, next) => {
  res.send("store fail")
  //next()
})

usersRouter.route("/users")
  .get((_, res) => res.send("users"))

productsRouter.route("/products")
  .get((_, res) => res.send("products"))

storeRouter.route("/store")
  .get((_, res) => res.send("store"))

app.use(usersRouter)
app.use(productsRouter)
app.use(storeRouter)

app.listen(80, () => console.log("running"))

But every time I request /store route it pass through productRouter middleware which is assigned only to it.

I can't understand this behavior.

Why is this? How can I manage independent middlewares for each one?

GET /store 200
products fail

Expected

GET /store 200
store fail

CodePudding user response：

When you do this:

app.use(productsRouter)

that sends ALL requests to the productsRouter and thus its middleware runs for all requests. So, when you have this:

productsRouter.use((_, res, next) => {
  res.send("products fail")
  //next()
});

That will run on every single request.

If you want the router to only see certain requests, then register the router on a path instead so the router only gets requests destined for a certain path.

app.use("/products", productsRouter)

And, then remove the path itself from the router's routes since the path will have already been filtered.

CodePudding user response：

In order to achieve the expected behavior, you will have to make little changes to your code.

First: Take this approach, since it will allow you to keep everything clean and separated (this is crucial if you want to implement specific middlewares for each route).

usersRouter.
  .get("/", (req, res) => res.send("users"))

productsRouter.route
  .get("/", (req, res) => res.send("products"))

storeRouter.route("/store")
  .get("/", (req, res) => res.send("store"))

app.use("/users", usersRouter)
app.use("/products", productsRouter)
app.use("/store", storeRouter)

Instead of this one

usersRouter.route("/users")
  .get((_, res) => res.send("users"))

productsRouter.route("/products")
  .get((_, res) => res.send("products"))

storeRouter.route("/store")
  .get((_, res) => res.send("store"))

app.use(usersRouter)
app.use(productsRouter)
app.use(storeRouter)

Second: Uncomment the next() call on your middlewares, identify the request parameter on their callbacks and store them in variables (not crucial, but improves readability)

const productsMiddleware = (req, res, next) => {
  res.send("products fail")
  next()
}

const storeMiddleware = (res, res, next) => {
  res.send("store fail")
  next()
}

Third: Pass the middleware you want to apply to a specific controller right after the route and before the actual controller declaration on your router. E.G.

usersRouter.
  .get("/", (req, res) => res.send("users"))

productsRouter.route
  .get("/", productsMiddleware, (req, res) => res.send("products"))

storeRouter.route("/store")
  .get("/", storeMiddleware, (req, res) => res.send("store"))

By doing all this things, you'll end up with "independent middlewares" that only apply to the specified route/controller.