Electron Take Up 100% Of Screen (Not Full Screen)

Use this:

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

let win

app.on('ready', () => {
   const {width, height} = electron.screen.getPrimaryDisplay().workAreaSize
   win = new BrowserWindow({width, height})
   win.loadURL('https://github.com')
})

use this!

win = new BrowserWindow({show: false});
win.maximize();
win.show();

Call mainWindow.maximize() to maximize the window after you create it.