不知要如何取得網址的JSON資訊

可以用 axios

若Q1問題解決EJS樣板如何配合AJAX達到即時更新效果

把你的 scan.js 改成類似這樣

var express = require('express');
var router = express.Router();
const fs = require('fs');
const axios = require('axios').default;
// middleware程式碼，這樣才能抓倒頁面資料
router.use(express.urlencoded({
    extended: false
  }));

router.use(express.json());

router.get('/', async (req, res) => {
  const response = await (await axios.get('http://127.0.0.1:8000/mesh/scan/get-data')).data;
  res.render('scan',{
    devices: response.devices,
  });
});

router.get('/get-data', (req, res) => {
  try {
    const scandata = JSON.parse(fs.readFileSync('./scandata.json', { encoding: 'utf-8' }));
    res.status(200).send({ devices: scandata.payload.devices });
  } catch (error) {
    console.log(error);
    res.status(500).send({ error }).end();
  }
});
module.exports = router;

result