// DevTools Console + Performance API 的最小诊断片段。
console.group('page diagnostics');
console.table(performance.getEntriesByType('navigation').map(entry => ({
  type: entry.type,
  domContentLoaded: Math.round(entry.domContentLoadedEventEnd),
  load: Math.round(entry.loadEventEnd),
})));
console.groupEnd();

new PerformanceObserver(list => {
  for (const entry of list.getEntries()) {
    console.log('long task', Math.round(entry.duration), 'ms', entry.name);
  }
}).observe({ type: 'longtask', buffered: true });