[lcp]
const po = new PerformanceObserver(() => {});
po.observe({type: 'largest-contentful-paint', buffered: true});
const lastEntry = po.takeRecords().slice(-1)[0];
return lastEntry.renderTime || lastEntry.loadTime;

[cls]
const po = new PerformanceObserver(() => {});
po.observe({type: 'layout-shift', buffered: true});
return po.takeRecords().reduce((val, entry) => val + entry.value, 0);

[fid]
const po = new PerformanceObserver(() => {});
po.observe({type: 'first-input', buffered: true});
const lastEntry = po.takeRecords().slice(-1)[0];
return lastEntry.processingStart - lastEntry.startTime;