Headless Chrome lighthouse with a subset of audits

intro.md

This is a simple script to run a few performance audits with Chrome's Lighthouse audit tool to help verify if you are making any performance improvements while coding.

It will print out an audit if it is outside of the given threshold; in green if it's improved or red if it hasn't.

Getting started

Run npm i -D lighthouse pretty-ms chalk
Run node test

test.js

const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');
const pretty = require('pretty-ms');
const chalk = require('chalk');
const log = console.log.bind(console.log);

(async () => {
  const chrome = await chromeLauncher.launch({chromeFlags: ['--headless']});
  const options = {
		logLevel: 'error',
		output: 'html', 
		port: chrome.port,
		onlyAudits: [
			'first-contentful-paint',
			'total-blocking-time',
			'first-meaningful-paint'
		]
	};
	const runnerResult = await lighthouse('https://localhost:8080', options);
	const attributes = [
		['first-contentful-paint', 2389.428],
		['total-blocking-time', 3795.761500000066],
		['first-meaningful-paint', 154633.9120000013],
	];
	attributes.forEach(([attribute, timeToBeat]) => {
		const attr = runnerResult.lhr.audits[attribute];
		const threshold = 0.02;
		if (attr.numericValue < (1-threshold) * timeToBeat) {
			log(attr.title, chalk.green(pretty(timeToBeat - attr.numericValue)));
		} else if (attr.numericValue > (1+threshold) * timeToBeat) {
			log(attr.title, chalk.red(pretty(attr.numericValue-timeToBeat)));
		}
	});
  await chrome.kill();
})();