require就是讀取外部檔案用的，通常是讀.js進來

主檔案myserver.js

myserver.js

const http = require('http');
const config = require('./config').config;

const server = http.createServer((req, res) => {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Hello World\n');
});

server.listen(config.port, config.hostname, () => {
    console.log(`Server running at http://${config.hostname}:${config.port}/`);
});

讀取config.js

const config = {
    hostname: '127.0.0.1',
    port: '3000'
};

exports.config = config;