server.js

// Copyright 2018 Google LLC.
// SPDX-License-Identifier: Apache-2.0

// server.js
// where your node app starts

// init project
const express        = require( 'express' );
var app              = express();
const fs             = require( 'fs' );
const lighthouse     = require( 'lighthouse' );
const puppeteer      = require('puppeteer')
const axios          = require( 'axios' );

app.get( '/', async ( req, res ) => {
  try {
    let target         = req.headers.referer;
    let responseTarget = req.query.response;
    let demoName       = req.query.demo;

    if ( ! target || '' === target || ! responseTarget || '' === responseTarget ) {
      res.status( 403 ).send( 'No domain passed on.' );
      return;
    }

    const chromeFlags = ['--headless', '--disable-dev-shm-usag', '--disable-gpu', '--disable-extensions', '--disable-popup-blocking', '--no-sandbox', '--single-process' ];

    res.send( 'Domain is being analysed.' );

    console.log( 'Launching Browser' );
    const chrome = await puppeteer.launch( { args: ['--no-sandbox'] } ).catch( error => { console.error( 'Chrome failed...', error ); } );

    const options = {
      logLevel: 'info', 
      disableStorageReset: true,
      maxWaitForLoad: 60000,
      chromeFlags: chromeFlags,
      onlyAudits: [
        'first-contentful-paint',
        'largest-contentful-paint',
        'max-potential-fid',
        'cumulative-layout-shift',
      ],
      port: ( new URL( chrome.wsEndpoint() ) ).port,
    };

    const config = {
      extends: 'lighthouse:default',
      settings: {
        onlyAudits: [
          'first-contentful-paint',
          'largest-contentful-paint',
          'max-potential-fid',
          'cumulative-layout-shift',
        ],
      },
    };

    console.log( 'Launching Lighthouse' );
    const runnerResult = await lighthouse( target, options, config ).catch( error => { console.error( 'Lighthouse failed...', error ); } );

    let data = {
      fcp : {
        score: runnerResult.lhr.audits['first-contentful-paint'].score,
        display: runnerResult.lhr.audits['first-contentful-paint'].displayValue,
      },
      lcp: {
        score:  runnerResult.lhr.audits['largest-contentful-paint'].score,
        display: runnerResult.lhr.audits['largest-contentful-paint'].displayValue,
      },
      fid: {
        score: runnerResult.lhr.audits['max-potential-fid'].score,
        display: runnerResult.lhr.audits['max-potential-fid'].displayValue,
      }, 
      cls: {
        score: runnerResult.lhr.audits['cumulative-layout-shift'].score,
        display: runnerResult.lhr.audits['cumulative-layout-shift'].displayValue,
      },
      score: runnerResult.lhr.categories.performance.score,
      demo_name: demoName,
    }

    await chrome.close().catch( error => { console.error( 'Closing chrome failed...', error ); } );

    axios.post( responseTarget, data ).then( ( res ) => {
      return;
    } ).catch( ( error ) => {
      console.error( error )
    } );

    return;
  } catch ( e ) {
     if ( 'undefined' !== typeof  chrome ) {
      await chrome.close().catch( error => { console.error( 'Closing chrome failed...', error ); } );
    }
    console.log( e );
  } finally {
    if ( 'undefined' !== typeof  chrome ) {
      await chrome.close().catch( error => { console.error( 'Closing chrome failed...', error ); } );
    }
  }
} );

// listen for requests :)
let port = process.env.PORT;
// let port = 64291;
var listener = app.listen( port, function() {
  console.log( 'Your app is listening on port ' + listener.address().port );
} );