express hello world
//to run : node filename.js
const express = require('express')
const app = express()
const port = 3000
app.get('/', (req, res) => res.send('Hello World!'))
app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))
//visit localhost:3000
// assuming you have done 1) npm init 2) npm install expressrequire express server.js
const express = require('express')const app = express() app.get('/', function (req, res) { res.send('Hello World')}) app.listen(3000)what is app.use() used for
//app.get will see only exact match ex.> "/book" here app.get will not allow /book/1, etc
//but app.use is different see below
//what is difference between app.use and app.all
//app.use takes only 1 callback while app.all takes multiple callbacks
//app.use will only see whether url starts with specified path But, app.all() will match the complete path
app.use( "/book" , middleware);
// will match /book
// will match /book/author
// will match /book/subject
app.all( "/book" , handler);
// will match /book
// won't match /book/author
// won't match /book/subject
app.all( "/book/*" , handler);
// won't match /book
// will match /book/author
// will match /book/subjectCopyright © 2021 Codeinu
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