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Kenneth Kim
3,795 PointsDifference Between Express.Router() and express() variables
//declarations
const express = require('express');
const app = express();
const router = express.Router();
//routers
app.get([path],[callback]);
router.get([path],[callback]);
In one of the questions in the quiz this was asked: "express.Router() creates an object that behaves similar to the app object."
The correct answer is 'True'. I know that we can both create routers by using either of the two but is it safe to say that they are not the same in all cases? If my understanding is correct, the express() variable can do more things like start a server while the other one cannot.
Can anyone provide a simple explanation so that I can understand when to use each of them? Thanks :)
(Please note the code above is not complete and are situated in several files. I just summarized how they are declared)
Kenneth Kim
3,795 PointsHi. The declarations is not in the proper format compared to what I have in my work space. I just did that to summarized :) Question was updated.
1 Answer
Nick Trabue
Courses Plus Student 12,666 Pointshttps://expressjs.com/en/guide/routing.html From the docs
express.Router Use the express.Router class to create modular, mountable route handlers. A Router instance is a complete middleware and routing system; for this reason, it is often referred to as a “mini-app”.
The following example creates a router as a module, loads a middleware function in it, defines some routes, and mounts the router module on a path in the main app.
Create a router file named birds.js in the app directory, with the following content:
var express = require('express')
var router = express.Router()
// middleware that is specific to this router
router.use(function timeLog (req, res, next) {
console.log('Time: ', Date.now())
next()
})
// define the home page route
router.get('/', function (req, res) {
res.send('Birds home page')
})
// define the about route
router.get('/about', function (req, res) {
res.send('About birds')
})
module.exports = router
Then, load the router module in the app:
var birds = require('./birds')
// ...
app.use('/birds', birds)
The app will now be able to handle requests to /birds and /birds/about, as well as call the timeLog middleware function that is specific to the route.
Doug Hawkinson
Full Stack JavaScript Techdegree Student 25,073 PointsNick:
I am a newbie in the Tech Degree program. I need a point of clarification on your comment above. Can I assume the the code in the first block goes in a file named something like router.js and the second block goes in app.js. I am having routing problems on Project 10 in the Tech degree program. I may just go ahead and post my problem and give folks a link to my github repo.
Harrison Cassedy
Java Web Development Techdegree Graduate 12,031 PointsHarrison Cassedy
Java Web Development Techdegree Graduate 12,031 PointsI may be wrong here but this is what I'm seeing.
it looks like you are using a compound expression. This means that there is a certain order to what should and is going to go first. This indicates the data type, access level, and scope. express is using parenthesis to indicate which field is going to go first by saying you need to have express before.
so what your code is saying in human speak: "Your first line of code says your application requires the Express.js dependency, the second line of code tells your app.js to use Express.js. The GET request is sent by the Express.js router to the server to retrieve data."
if this helps please upvote :)