获取fp、fcp时间

const observer = new PerformanceObserver((list) => {
  console.log("list", list);
  const entries = list.getEntries();
  for (const entry of entries) {
    console.log("entry", entry.name);
    if (entry.name === "first-paint") {
      const whiteScreen = entry.startTime;
      console.log("fp", whiteScreen);
    } else if (entry.name === "first-contentful-paint") {
      console.log("fcp", entry.startTime);
    }
  }
});

observer.observe({ type: "paint", buffered: true });