Time to open an electron window.

index.html

<div class="times"></div>
<script>
  const now = Date.now();
  setTimeout(function () {
    const div = document.querySelector('.times');
    const search = location.search.substring(1).split('&').map(pair => pair.split('=')).reduce((carry, [key, value]) => {
      carry[key] = Number(value);
      return carry;
    }, {});

    const render = Date.now();
    div.innerHTML = `Time to start main process JS: ${search.main}
    <br/>Time to create window: ${search.window} (${search.window - search.main})
    <br/>Time to execute first client script: ${now} (${now - search.window})
    <br/>Time to first render: ${render} (${render - now})`;
  });
</script>

index.js

const mainStart = Date.now();

const electron = require('electron');

electron.app.on('ready', function() {
    const window = new electron.BrowserWindow({
        width: 640,
        height: 480
    });
    window.loadURL(`file://${__dirname}/index.html?main=${mainStart}&window=${Date.now()}`);
});

package.json

{
  "name": "electron-start",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "electron": "^5.0.6"
  }
}