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Learn Express Routers
Express.Router

An Express router provides a subset of Express methods. To create an instance of one, we invoke the .Router() method on the top-level Express import.

To use a router, we mount it at a certain path using app.use() and pass in the router as the second argument. This router will now be used for all paths that begin with that path segment. To create a router to handle all requests beginning with /monsters, the code would look like this:

const express = require('express'); const app = express(); const monsters = { '1': { name: 'godzilla', age: 250000000 }, '2': { Name: 'manticore', age: 21 } } const monstersRouter = express.Router(); app.use('/monsters', monstersRouter); monstersRouter.get('/:id', (req, res, next) => { const monster = monsters[req.params.id]; If (monster) { res.send(monster); } else { res.status(404).send(); } });

Inside the monstersRouter, all matching routes are assumed to have /monsters prepended, as it is mounted at that path. monstersRouter.get('/:id') matches the full path /monsters/:id.

When a GET /monsters/1 request arrives, Express matches /monsters in app.use() because the beginning of the path ('/monsters') matches. Express’ route-matching algorithm enters the monstersRouter‘s routes to search for full path matches. Since monstersRouter.get('/:id) is mounted at /monsters, the two paths together match the entire request path (/monsters/1), so the route matches and the callback is invoked. The 'godzilla' monster is fetched from the monsters array and sent back.

Instructions

1.

Create an expressionsRouter instance of Express.Router. Mount it at /expressions at your base app level with app.use.

After doing so, create a route for your expressionsRouter that will send all expressions for a GET request.

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