性能测试工具｜如何有效度量前端性能-JS 代码提取

new PerformanceObserver((entryList) => {
 for (const entry of entryList.getEntriesByName('first-contentful-paint')) {
   console.log('FCP candidate:', entry.startTime, entry);
 }}).observe({type: 'paint', buffered: true});