evaluate(pageFunction[, arg])

import { browser } from 'k6/experimental/browser';
import { check } from 'k6/http';

export const options = {
  scenarios: {
    browser: {
      executor: 'shared-iterations',
      options: {
        browser: {
            type: 'chromium',
        },
      },
    },
  },
}

export default async function () {
  const page = browser.newPage();
  
  await page.goto('https://test.k6.io/browser.php');
  const dimensions = page.evaluate(() => {
    const obj = {
      width: document.documentElement.clientWidth,
      height: document.documentElement.clientHeight,
      deviceScaleFactor: window.devicePixelRatio
    };
    return obj;
  });

  check(dimensions, {
    'width': d => d.width === 1280,
    'height': d => d.height === 720,
    'scale': d => d.deviceScaleFactor === 1,
  });
}