electron/docs/fiddles/windows/manage-windows/frameless-window/renderer.js

const { ipcRenderer } = require('electron/renderer')

const newWindowBtn = document.getElementById('frameless-window')

newWindowBtn.addEventListener('click', () => {
  const url = 'data:text/html,<h2>Hello World!</h2><a id="close" href="javascript:window.close()">Close this Window</a>'
  ipcRenderer.send('create-frameless-window', { url })
})