Send a response from a function to route in expressjs code example

Example 1: 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 express

Example 2: widlicard in express router

//This route path will match acd and abcd.
app.get('/ab?cd', function (req, res) {
  res.send('ab?cd')
})
//This route path will match abcd, abbcd, abbbcd, and so on.
app.get('/ab+cd', function (req, res) {
  res.send('ab+cd')
})
//This route path will match abcd, abxcd, abRANDOMcd, ab123cd, and so on.
app.get('/ab*cd', function (req, res) {
  res.send('ab*cd')
})
//This route path will match /abe and /abcde.
app.get('/ab(cd)?e', function (req, res) {
  res.send('ab(cd)?e')
})
//This route path will match anything with an “a” in it.
app.get(/a/, function (req, res) {
  res.send('/a/')
})
//This route path will match butterfly and dragonfly, 
//but not butterflyman, dragonflyman, and so on.
app.get(/.*fly$/, function (req, res) {
  res.send('/.*fly$/')
})