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JS coverage profiler data via protocol
'use strict';
const chromeLauncher = require('chrome-launcher');
const CDP = require('chrome-remote-interface');
const launchChrome = () =>
chromeLauncher.launch({
chromeFlags: ['--disable-gpu', '--headless']
});
launchChrome()
.then(async chrome => {
const protocol = await CDP({port: chrome.port});
try {
const {Page, Profiler} = protocol;
await Profiler.enable();
await Page.enable();
await Profiler.startPreciseCoverage();
Page.navigate({url: 'https://paulirish.com/'});
await Page.loadEventFired();
const res = await Profiler.takePreciseCoverage();
await Profiler.stopPreciseCoverage();
const coverage = calculateCoverage(res);
console.log(coverage);
} catch (err) {
console.error(err);
} finally {
protocol.close();
chrome.kill();
}
})
.catch(err => console.error(err));
// `calculateCoverage` is roughly stolen from https://github.com/joelgriffith/navalia/blob/master/src/Chrome.ts
// Haven't looked closely but handling these offsets is hard, so I'm dubious the below is correct
// Here is the DevTools' equivalent: https://github.com/ChromeDevTools/devtools-frontend/blob/master/front_end/coverage/CoverageModel.js
// see _processJSCoverage()
function calculateCoverage(res) {
const src = 'https://www.youtube.com/yts/jsbin/www-embed-player-vflOvovMJ/www-embed-player.js';
const scriptCoverage = res.result.find(script => script.url === src);
if (!scriptCoverage) {
console.log(`:coverage() > ${src} not found on the page.`);
return new Error(`Couldn't locat script ${src} on the page.`);
}
if (scriptCoverage && scriptCoverage.functions && scriptCoverage.functions.length) {
const coverageData = scriptCoverage.functions.reduce(
(fnAccum, coverageStats) => {
const functionStats = coverageStats.ranges.reduce(
(rangeAccum, range) => {
return {
total: range.endOffset > rangeAccum.total ? range.endOffset : rangeAccum.total,
unused:
rangeAccum.unused + (range.count === 0 ? range.endOffset - range.startOffset : 0)
};
},
{
total: 0,
unused: 0
}
);
return {
total: functionStats.total > fnAccum.total ? functionStats.total : fnAccum.total,
unused: fnAccum.unused + functionStats.unused
};
},
{
total: 0,
unused: 0
}
);
return Object.assign(coverageData, {
percentUnused: coverageData.unused / coverageData.total
});
}
return Error('unexpected');
}
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