安裝套件

npm init -y
npm i express
npm i -D nodemon

index.js

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

app.get('/', (req, res) => {
  res.send('hello');
});

app.listen(port, () => {
  console.log('server start');
});

修改npm script

scripts: {
  "dev": "nodemon index.js"
}

執行npm script

npm run dev