Zizzamia/perfume.js

import { fcp, tbt, ntbt } from './metrics';
import { IPerformanceEntry } from './types';

export const initTotalBlockingTime = (
  performanceEntries: IPerformanceEntry[],
): void => {
  performanceEntries.forEach(entry => {
    if (entry.name !== 'self' || entry.startTime < fcp.value) {
      return;
    }
    const blockingTime = entry.duration - 50;
    if (blockingTime > 0) {
      tbt.value += blockingTime;
      ntbt.value += blockingTime;
    }
  });
};