Lighthouse score for different network throttling

throttle_effect_on_score.js

const fs = require('fs');
const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');

(async () => {
  const chrome = await chromeLauncher.launch();
  const options = {logLevel: 'info', output: 'json', onlyCategories: ['performance'], port: chrome.port};
  const DEVTOOLS_RTT_ADJUSTMENT_FACTOR = 3.75;
  const DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR = 0.9;
  const mobileRegular3g = {
    extends: 'lighthouse:default',
    settings: {
      maxWaitForFcp: 15 * 1000,
      maxWaitForLoad: 35 * 1000,
      emulatedFormFactor: 'desktop',
      throttling:  {
        rttMs: 300,
        throughputKbps: 700,
        requestLatencyMs: 300 * DEVTOOLS_RTT_ADJUSTMENT_FACTOR,
        downloadThroughputKbps: 700 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
        uploadThroughputKbps: 700 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
      }
    }
  };
  const mobileSlow4G = {
    extends: 'lighthouse:default',
    settings: {
      maxWaitForFcp: 15 * 1000,
      maxWaitForLoad: 35 * 1000,
      emulatedFormFactor: 'desktop',
      throttling:  {
        rttMs: 150,
        throughputKbps: 1.6 * 1024,
        requestLatencyMs: 150 * DEVTOOLS_RTT_ADJUSTMENT_FACTOR,
        downloadThroughputKbps: 1.6 * 1024 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
        uploadThroughputKbps: 750 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
      }
    }
  };
  const desktopDense4g = {
    extends: 'lighthouse:default',
    settings: {
      maxWaitForFcp: 15 * 1000,
      maxWaitForLoad: 35 * 1000,
      emulatedFormFactor: 'desktop',
      throttling:  {
        rttMs: 40,
        throughputKbps: 10 * 1024,
        requestLatencyMs: 0,
        downloadThroughputKbps: 0,
        uploadThroughputKbps: 0,
      }
    }
  };
  const runnerResult = await lighthouse('https://browserstack.com', options, mobileRegular3g);

  // `.report` is the HTML report as a string
  const report = runnerResult.report;
  fs.writeFileSync('finalReport.json', report);

  // `.lhr` is the Lighthouse Result as a JS object
  console.log('Report is done for', runnerResult.lhr.finalUrl);
  console.log('Performance score was', runnerResult.lhr.categories.performance.score * 100);

  await chrome.kill();
})();