Author:
** Backend Routing**⚓︎
Definiton⚓︎
When? (background)
client requests to a particular endpoint
[ <=> URI
+ HTTP
request method (GET
, POST
, ...) ].
What? (import routing)
To handle the request, in backend routing
, the server handles every request by responding to the client with a code 201
(I got that thing you want!) or a 404
(Nope, I don’t have that!).
Situation? (example)
Let’s say a user fills out a form with his name, address, favorite hobby and sends a POST
request by submitting the form. That GET request url
is sent to the server, and the server serves back the requested url
to the client as a static file that is stored on the server.
If the server doesn’t have the requested file, then it returns a 404
response error.
Usage⚓︎
Code using
Express.js syntax
app.METHOD(PATH, HANDLER)
app
: an instance of express.METHOD
: an HTTP request method, in lowercase.PATH
: a path on the server.HANDLER
: the function executed when the route is matched.
Example code
//Respond with Hello World! on the homepage: app.get('/', (req, res) => { res.send('Hello World!') })
//Respond to POST request on the root route (/), the application’s home page: app.post('/', (req, res) => { res.send('Got a POST request') })
//Respond to a PUT request to the /user route: app.put('/user', (req, res) => { res.send('Got a PUT request at /user') })
//Respond to a DELETE request to the /user route: app.delete('/user', (req, res) => { res.send('Got a DELETE request at /user') })
Handlers for Routing⚓︎
Open the boxes below to see the examples 👇
Four classes of handler
1° A single callback function
can handle a route
const express = require('express') const app = express() const port = 3000 app.get('/', (req, res) => { res.send('Hello from A!') }) app.listen(port, () => { console.log(`Example app listening on port ${port}`) })
2° More than one callback function
can handle a route (use next()
to control the next callback.)
const express = require('express') const app = express() const port = 3000 app.get('/', (req, res, next) => { console.log('the response will be sent by the next function ...') next() }, (req, res) => { res.send('Hello from B!') }) app.listen(port, () => { console.log(`Example app listening on port ${port}`) })
3° An array of callback functions
can handle a route
const express = require('express') const app = express() const port = 3000 const cb0 = function (req, res, next) { console.log('CB0') next() } const cb1 = function (req, res, next) { console.log('CB1') next() } const cb2 = function (req, res) { res.send('Hello from C!') } app.get('/', [cb0, cb1, cb2]) app.listen(port, () => { console.log(`Example app listening on port ${port}`) })
4° A combination of independent functions and arrays of functions
can handle a route
const express = require('express') const app = express() const port = 3000 const cb0 = function (req, res, next) { console.log('CB0') next() } const cb1 = function (req, res, next) { console.log('CB1') next() } app.get('/', [cb0, cb1], (req, res, next) => { console.log('the response will be sent by the next function ...') next() }, (req, res) => { res.send('Hello from D!') }) app.listen(port, () => { console.log(`Example app listening on port ${port}`) })
References:⚓︎
Last update:
February 27, 2023 00:42:01
Created: December 4, 2022 01:47:38
Created: December 4, 2022 01:47:38