A new feature of the Reporting API gives developers more insight into the functioning of their code on client machines. The ReportingObserver API allows JavaScript to capture reports in callback, which can be used to save custom reporting data to page analytics.
Docs: https://github.com/W3C/reporting/blob/master/EXPLAINER.md#reportingobserver---observing-reports-from-javascript https://developers.google.com/web/updates/2018/07/reportingobserver
Samples: https://developers.google.com/web/updates/2018/07/reportingobserver?hl=en#examples