main.js

const { app, BrowserWindow } = require('electron')
const path = require('path')
const url = require('url')

let mainWindow

function createWindow() {

    mainWindow = new BrowserWindow({
        width: 800,
        height: 600,
        backgroundColor: "#ccc",
        icon: __dirname + '/icon.png',
        webPreferences: {
            nodeIntegration: true, // to allow require
            contextIsolation: false, // allow use with Electron 12+
            preload: path.join(__dirname, 'preload.js')
        }
    })

    mainWindow.webContents.on('new-window', function (e, url) {
        e.preventDefault();
        require('electron').shell.openExternal(url);
    });


    mainWindow.loadURL(url.format({
        pathname: path.join(__dirname, 'index.html'),
        protocol: 'file:',
        slashes: true
    }))

    mainWindow.on('closed', function () {
        mainWindow = null
    })
}

app.on('ready', createWindow)
app.on('window-all-closed', function () {
    app.quit()
})

app.on('activate', function () {
    if (mainWindow === null) {
        createWindow()
    }
})

app.whenReady().then(() => {
  protocol.registerFileProtocol('atom', (request, callback) => {
    const url = request.url.substr(7)
    callback({ path: path.normalize(`${__dirname}/${url}`) })
  })
})