Lighthouse Cron

Cron multiple batch Lighthouse audits and emit results for sending to remote server.

Want to track your Lighthouse scores and metrics overtime? This module will allow you to write a simple script to perform multiple audits over time and allow you to transport the results.

Set up

npm install --save lighthouse-cron

Usage

const LighthouseCron = require('lighthouse-cron');
const lighthouseCron = new LighthouseCron(
  [
    {
      url: 'https://www.google.com/'
    }
  ],
  '00 00,15,30,45 * * * 0-6'
);
 
lighthouseCron.on('auditComplete', audit => {
  console.log(audit);
});
 
lighthouseCron.init();

Reference

new LighthouseCron(urls, cron, timezone, chromeFlags, lighthouseFlags, lighthouseConfig)

Create a new instance of lighthouse cron.

Parameters

• urls - Required. Array of objects including the url as a property.
• cron - String for cron pattern (Default: '00 00 * * * 0-6')
• timezone - String for cron timezone (Default: 'Europe/London')
• chromeFlags - Array of Chrome flags e.g. ['--headless']
• lighthouseFlags - Object to enable Lighthouse flags
• lighthouseConfig - Object describe custom configurations for lighthouse runs

init(autorun)

Initialise lighthouse cron.

Parameters

• autorun - Boolean for if cron should do first run instantly (Default: false)

Events

auditComplete

After a lighthouse audit is complete on a url this event returns the results.

cronCycleComplete

After the cron job has been complete an event is emitted.

allAuditsComplete

After all lighthouse audits are complete an event is emitted.

error

If a an error occurs an event is emitted with the error returned.

Examples

Below is an example of how you could report performance metrics and lighthouse scores to the data analytics platform Keen.io.

const KeenTracking = require('keen-tracking');
const LighthouseCron = require('lighthouse-cron');
 
// Configuring Keen client
const keenClient = new KeenTracking({
  projectId: 'Your Project Id',
  writeKey: 'Your Write Key'
});
 
// Additional website and description fields added to improve your dashboards
const lighthouseCron = new LighthouseCron(
  [
    {
      website: 'Google',
      description: 'Homepage',
      url: 'https://www.google.com'
    },
    {
      website: 'YouTube',
      description: 'Homepage',
      url: 'https://www.youtube.com'
    }
  ],
  '00 00 * * * 0-6'
);
 
// listening for each audit to be complete
lighthouseCron.on('auditComplete', audit => {
  const report = generateTrackableReport(audit);
  keenClient.recordEvent('lighthouse audits', report);
});
 
 
// Pulling out the metrics we are interested in
function generateTrackableReport(audit) {
  const reports = [
    'first-meaningful-paint',
    'speed-index-metric',
    'estimated-input-latency',
    'time-to-interactive',
    'total-byte-weight',
    'dom-size'
  ];
 
  const obj = {
    metadata: audit.metadata,
    score: Math.round(audit.score),
    results: {}
  };
 
  reports.forEach(report => {
    obj.results[report] = getRequiredAuditMetrics(audit.results.audits[report]);
  });
  return obj;
}
 
// getting the values we interested in
function getRequiredAuditMetrics(metrics) {
  return {
    score: metrics.score,
    value: metrics.rawValue,
    optimal: metrics.optimalValue
  };
}
 
lighthouseCron.init();

This demo is also available to be run from this module however instead of reporting the metrics to Keen.io they are just printed to console.

npm run demo