static compute()

in src/sdk/trace-metrics.ts [34:86]

• 44 lines of code
• 11 McCabe index (conditional complexity)

  static compute(trace: LHProcessedTrace) {
    const { processEvents } = trace;
    const measuresMap = new Map();
    const userTimings: Array<TraceOutput> = [];

    for (const event of processEvents) {
      const { name, ph, ts, args } = event;

      if (!event.cat.includes('blink.user_timing')) {
        continue;
      }
      // discard all browser level mark events with frame data
      if (
        name === 'requestStart' ||
        name === 'navigationStart' ||
        name === 'paintNonDefaultBackgroundColor' ||
        args.frame !== undefined
      ) {
        continue;
      }

      /**
       * user timing mark events falls under `R` and i or I
       * measure events starts with `b` and ends with `e`
       * Doc - https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/edit#heading=h.puwqg050lyuy
       */
      const phase = ph.toLowerCase();
      if (phase === 'r' || phase === 'i') {
        userTimings.push({
          name,
          type: 'mark',
          start: {
            us: ts,
          },
        });
      } else if (phase === 'b') {
        measuresMap.set(name, ts);
      } else if (phase === 'e') {
        const startTime = measuresMap.get(name);
        userTimings.push({
          name,
          type: 'measure',
          start: {
            us: startTime,
          },
          duration: {
            us: ts - startTime,
          },
        });
      }
    }
    return userTimings;
  }