lighthouse-metrics.js

const lighthouse = require('lighthouse');
const puppeteer = require('puppeteer');

const chromeLauncher = require('chrome-launcher');
const reportGenerator = require('lighthouse/lighthouse-core/report/report-generator');
const request = require('request');
const util = require('util');

const options = {
  logLevel: 'info',
  disableDeviceEmulation: true,
  chromeFlags: ['--disable-mobile-emulation'],
};

/**
 *
 * Perform a Lighthouse run
 * @param {String} url - url The URL to test
 * @param {Object} options - Optional settings for the Lighthouse run
 * @param {Object} [config=null] - Configuration for the Lighthouse run. If
 * not present, the default config is used.
 */
async function lighthouseFromPuppeteer(url, options, config = null) {
  // Launch chrome using chrome-launcher
  const chrome = await chromeLauncher.launch(options);
  options.port = chrome.port;

  // Connect chrome-launcher to puppeteer
  const resp = await util.promisify(request)(`http://localhost:${options.port}/json/version`);
  const {webSocketDebuggerUrl} = JSON.parse(resp.body);
  const browser = await puppeteer.connect({browserWSEndpoint: webSocketDebuggerUrl});

  // Run Lighthouse
  const {lhr} = await lighthouse(url, options, config);
  await browser.disconnect();
  await chrome.kill();

  const json = reportGenerator.generateReport(lhr, 'json');

  const audits = JSON.parse(json).audits; // Lighthouse audits
  const firstContentfulPaint = audits['first-contentful-paint'].displayValue;
  const totalBlockingTime = audits['total-blocking-time'].displayValue;
  const timeToInteractive = audits['interactive'].displayValue;

  console.log(`\n
     Lighthouse metrics: 
     🎨 First Contentful Paint: ${firstContentfulPaint}, 
     ⌛️ Total Blocking Time: ${totalBlockingTime},
     👆 Time To Interactive: ${timeToInteractive}`);
}

lighthouseFromPuppeteer('https://bbc.com', options);