lighthouse
Version:
Automated auditing, performance metrics, and best practices for the web.
44 lines (34 loc) • 1.14 kB
JavaScript
/**
* @license
* Copyright 2017 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview Tracks unused CSS rules.
*/
import BaseGatherer from '../base-gatherer.js';
class CSSUsage extends BaseGatherer {
/** @type {LH.Gatherer.GathererMeta} */
meta = {
supportedModes: ['snapshot', 'navigation'],
};
/**
* @param {LH.Gatherer.Context} context
* @return {Promise<LH.Artifacts['CSSUsage']>}
*/
async getArtifact(context) {
const session = context.driver.defaultSession;
const executionContext = context.driver.executionContext;
await session.sendCommand('DOM.enable');
await session.sendCommand('CSS.enable');
await session.sendCommand('CSS.startRuleUsageTracking');
// Force style to recompute.
// Doesn't appear to be necessary in newer versions of Chrome.
await executionContext.evaluateAsync('getComputedStyle(document.body)');
const {ruleUsage} = await session.sendCommand('CSS.stopRuleUsageTracking');
await session.sendCommand('CSS.disable');
await session.sendCommand('DOM.disable');
return ruleUsage;
}
}
export default CSSUsage;