Sample Electron Main.js file.

main.js

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

require('dotenv').config();

let win = null;

function createWindow() {
  // Initialize the window to our specified dimensions
  win = new BrowserWindow({ width: 1000, height: 600 });

  // Specify entry point
  if (process.env.PACKAGE === 'true') {
    win.loadURL(
      url.format({
        pathname: path.join(__dirname, process.env.DISTPATH),
        protocol: 'file:',
        slashes: true
      })
    );
  } else {
    win.loadURL(process.env.HOST);
    win.webContents.openDevTools();
  }

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

app.on('ready', function() {
  createWindow();
});

app.on('activate', () => {
  if (win === null) {
    createWindow();
  }
});

app.on('window-all-closed', function() {
  if (process.platform != 'darwin') {
    app.quit();
  }
});