main.js

const { app, BrowserWindow } = require("electron");

let mainWindow;

function createWindow() {
  mainWindow = new BrowserWindow({
    width: 500,
    height: 500,
    transparent: true,
    frame: false,
    alwaysOnTop: true,
    // workaround for Mojave dark mode
    // refs. https://github.com/electron/electron/issues/13164
    titleBarStyle: "customButtonsOnHover",
    webPreferences: {
      nodeIntegration: true
    }
  });

  mainWindow.loadFile("index.html");

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

  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;
  });
}

app.on("ready", 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.