import App from 'next/app' if (typeof navigator !== 'undefined') { window.__BEACONS = window.__BEACONS || [] navigator.sendBeacon = async function () { const args = await Promise.all( [...arguments].map((v) => { if (v instanceof Blob) { return v.text() } return v }) ) window.__BEACONS.push(args) } } export default class MyApp extends App {} export function reportWebVitals(data) { navigator.sendBeacon('/test', new URLSearchParams(data).toString()) }