当使用Express Router时，这两行等效吗？

Question

I could not find the official docs in a google search . Where are the official API docs for express.Router() and are lines 1 and 2 the same?

If so, is it just a matter of preference on which to use?

const express = require('express');
const router = express.Router();

router.get('path', callback); // line 1
router.route('path').get(callback); // line 2

Answer 1

There are 3 ways with which you can declare routes in your application

These are:

1. app.get("path", fn)
2. router.get("path", fn)
3. router.route("path").get(fn)

All of the above functions are used to generate http request routes in your application.

The app.get is the most basic one and is not recommended for larger projects. The reason being it gives less flexibility in handling routes as compared to the express.router . In express applications you will be dealing with middlewares a lot. Middlewares are functions that are executed before the controller function of your application

For example, take a look at this line

app.get("/user", verifyUser, createUser) ;`

Above, verifyUser is a middleware function that is called with (Request, Response, Next) arguments by the express framework, you can write your incoming request verification logic in verifyUser and can then call NextFunction to pass the control to the next function with is the createUser controller ;

You can have as many middlewares as you want in your route declaration.

What if you need to call verifyUser each time a user is created, removed, fetched or modified. For each of the actions, you need to define your routes like this:

  app.get("/user", verifyUser, fetchUser);
  app.put("/user", verifyUser, updateUser);
  app.post("/user", verifyUser, createUser);
  app.delete("/user", verifyUser, deleteUser);

In larger applications you need to defined different logics to different entities and routes.

express.router solves the above problem by providing us a flexibility to define what to do when user lands the /user route before passing the request to the middleware.

The above code in express router can be written as follows:

  // file: userRoutes.js
  const router = express.Router();

  router.use((req, res, next) => {
     verifyUser(req, res, next);
  });

  function verifyUser(req, res, next) {
    // verification logic here
    if (/** verification is successful */)
      return next(); // return to the controller
    res.status(400).json({ msg: "user does not exists" });
  }

  router.get("/user", fetchUser);
  router.put("/user", updateUser);
  router.post("/user", createUser);
  router.delete("/user", deleteUser);

  module.exports = router;

  // app.js
  const userRoutes = require("./userRoutes");
  app.use(userRoutes);

Things gets really simplified if we chain the http request methods in the following way:

  router.route("/user")
        .get(fetchUser);
        .put(updateUser);
        .post(createUser);
        .delete(deleteUser);

Note: Above code is for explanation purpose only, there may be syntax errors, the code is not expected to run as it is. User might need to alter the code to make it work.