index.js

const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => {
  res.send('Hello World!')
})

// POST method route
app.post('/', function (req, res) {
  res.send('POST request to the homepage');
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
})

package.json

{
  "name": "first-api",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.17.1"
  }
}

• https://expressjs.com/zh-tw/guide/routing.html
• https://expressjs.com/zh-tw/starter/hello-world.html