afrontend/main.js

## main.js
const electron = require('electron')
// Module to control application life.
const app = electron.app
// Module to create native browser window.
const BrowserWindow = electron.BrowserWindow

const path = require('path')
const url = require('url')

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the JavaScript object is garbage collected.
let mainWindow

function createWindow () {
  // Create the browser window.
  mainWindow = new BrowserWindow({width: 800, height: 600})

  // and load the popup.html of the app.
  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'popup.html'),
    protocol: 'file:',
    slashes: true
  }))

  // Open the DevTools.
  // mainWindow.webContents.openDevTools()

  // Emitted when the window is closed.
  mainWindow.on('closed', function () {
    // Dereference the window object, usually you would store windows
    // in an array if your app supports multi windows, this is the time
    // when you should delete the corresponding element.
    mainWindow = null
  })
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.on('ready', createWindow)

// Quit when all windows are closed.
app.on('window-all-closed', function () {
  // On OS X it is common for applications and their menu bar
  // to stay active until the user quits explicitly with Cmd + Q
  if (process.platform !== 'darwin') {
    app.quit()
  }
})

app.on('activate', function () {
  // On OS X it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (mainWindow === null) {
    createWindow()
  }
})

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

## package.json
{
    "name": "Reading Web Data Example",
    "description": "This extension shows a current temperature of the seoul",
    "version": "1.0",
    "main": "main.js"
}

## popup.html
<!DOCTYPE html>
<html>
  <head>
    <title>서울 기온</title>
    <meta charset="utf-8" />
    <style type="text/css">
    .box {
      width: 120px;
      height: 14px;
      line-height: 14px;
      font-size: 14px;
      color: brown;
    }

    .box > span {
      color: red
    }
    </style>
    <script src="popup.js"></script>
  </head>
  <body>
    <div class="box">서울의 온도 <span id="temperature">0 도</span></div>
  </body>
</html>

## popup.js
document.addEventListener('DOMContentLoaded', function () {
  httpRequest = new XMLHttpRequest();
  httpRequest.onreadystatechange = getContents;
  httpRequest.open('GET', 'https://www.accuweather.com/ko/kr/seoul/226081/weather-forecast/226081');
  httpRequest.send();

  function getElement(html) {
    var div = document.createElement('div');
    div.innerHTML = html;
    return div;
  }

  function parseHTML(html) {
    var el = getElement(html);
    var temp = el.querySelector('#current-city-tab > a > span.local-temp').innerHTML;
    document.querySelector('#temperature').innerHTML = temp;
  }

  function getContents() {
    if (httpRequest.readyState === 4) {
      if (httpRequest.status === 200) {
        parseHTML(httpRequest.responseText);
      } else {
        document.querySelector('.box').innerHTML = '온도 읽기 실패';
      }
    }
  }
});
	const electron = require('electron')
	// Module to control application life.
	const app = electron.app
	// Module to create native browser window.
	const BrowserWindow = electron.BrowserWindow

	const path = require('path')
	const url = require('url')

	// Keep a global reference of the window object, if you don't, the window will
	// be closed automatically when the JavaScript object is garbage collected.
	let mainWindow

	function createWindow () {
	// Create the browser window.
	mainWindow = new BrowserWindow({width: 800, height: 600})

	// and load the popup.html of the app.
	mainWindow.loadURL(url.format({
	pathname: path.join(__dirname, 'popup.html'),
	protocol: 'file:',
	slashes: true
	}))

	// Open the DevTools.
	// mainWindow.webContents.openDevTools()

	// Emitted when the window is closed.
	mainWindow.on('closed', function () {
	// Dereference the window object, usually you would store windows
	// in an array if your app supports multi windows, this is the time
	// when you should delete the corresponding element.
	mainWindow = null
	})
	}

	// This method will be called when Electron has finished
	// initialization and is ready to create browser windows.
	// Some APIs can only be used after this event occurs.
	app.on('ready', createWindow)

	// Quit when all windows are closed.
	app.on('window-all-closed', function () {
	// On OS X it is common for applications and their menu bar
	// to stay active until the user quits explicitly with Cmd + Q
	if (process.platform !== 'darwin') {
	app.quit()
	}
	})

	app.on('activate', function () {
	// On OS X it's common to re-create a window in the app when the
	// dock icon is clicked and there are no other windows open.
	if (mainWindow === null) {
	createWindow()
	}
	})

	// In this file you can include the rest of your app's specific main process
	// code. You can also put them in separate files and require them here.
	{
	"name": "Reading Web Data Example",
	"description": "This extension shows a current temperature of the seoul",
	"version": "1.0",
	"main": "main.js"
	}