Electron + create-react-app setup

electron.js

const {app, BrowserWindow} = require("electron")
const path = require("path")
const isDev = require("electron-is-dev")

let mainWindow // prevent main windows to be garbage collected

function createWindow() {
  mainWindow = new BrowserWindow({
    frame: false,
    width: 226,
    height: 137,
    skipTaskbar: true,
    transparent: true,
    icon: path.join(__dirname, "icons/64x64.png"),
  })
  
  mainWindow.setAlwaysOnTop(true)
  mainWindow.setVisibleOnAllWorkspaces(true)

  if (isDev) {
    // connect to create-react-app dev server
    mainWindow.loadURL("http://localhost:3000")
  }
  else {
    // use package build file
    mainWindow.loadURL(`file://${path.join(__dirname, "../build/index.html")}`)
  }

  mainWindow.on("closed", function () {
    mainWindow = null // release the main windows for garbage collection
  })
}

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()
  }
})