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分析

Next.js 内置了对测量和报告性能指标的支持。你可以使用 useReportWebVitals 钩子自行管理报告，或者 Vercel 提供 托管服务 来自动为你收集和可视化指标。

¥Next.js has built-in support for measuring and reporting performance metrics. You can either use the useReportWebVitals hook to manage reporting yourself, or alternatively, Vercel provides a managed service to automatically collect and visualize metrics for you.

构建你自己的​

¥Build Your Own

'use client'

import { useReportWebVitals } from 'next/web-vitals'

export function WebVitals() {
  useReportWebVitals((metric) => {
    console.log(metric)
  })
}
import { WebVitals } from './_components/web-vitals'

export default function Layout({ children }) {
  return (
    <html>
      <body>
        <WebVitals />
        {children}
      </body>
    </html>
  )
}

由于 useReportWebVitals 钩子需要 "use client" 指令，因此性能最佳的方法是创建根布局导入的单独组件。这将客户端边界专门限制为 WebVitals 组件。

¥Since the useReportWebVitals hook requires the "use client" directive, the most performant approach is to create a separate component that the root layout imports. This confines the client boundary exclusively to the WebVitals component.

查看 API 参考 了解更多信息。

¥View the API Reference for more information.

网络生命体​

¥Web Vitals

网络生命体 是一组有用的指标，旨在捕捉网页的用户体验。以下 Web Vitals 均包含在内：

¥Web Vitals are a set of useful metrics that aim to capture the user experience of a web page. The following web vitals are all included:

你可以使用 name 属性处理这些指标的所有结果。

¥You can handle all the results of these metrics using the name property.

'use client'

import { useReportWebVitals } from 'next/web-vitals'

export function WebVitals() {
  useReportWebVitals((metric) => {
    switch (metric.name) {
      case 'FCP': {
        // handle FCP results
      }
      case 'LCP': {
        // handle LCP results
      }
      // ...
    }
  })
}
'use client'

import { useReportWebVitals } from 'next/web-vitals'

export function WebVitals() {
  useReportWebVitals((metric) => {
    switch (metric.name) {
      case 'FCP': {
        // handle FCP results
      }
      case 'LCP': {
        // handle LCP results
      }
      // ...
    }
  })
}

将结果发送到外部系统​

¥Sending results to external systems

你可以将结果发送到任何端点，以测量和跟踪站点上的真实用户性能。例如：

¥You can send results to any endpoint to measure and track real user performance on your site. For example:

useReportWebVitals((metric) => {
  const body = JSON.stringify(metric)
  const url = 'https://example.com/analytics'

  // Use `navigator.sendBeacon()` if available, falling back to `fetch()`.
  if (navigator.sendBeacon) {
    navigator.sendBeacon(url, body)
  } else {
    fetch(url, { body, method: 'POST', keepalive: true })
  }
})

很高兴知道：如果你使用 谷歌分析，则使用 id 值可以让你手动构建度量分布（以计算百分位数等）

¥Good to know: If you use Google Analytics, using the id value can allow you to construct metric distributions manually (to calculate percentiles, etc.)

useReportWebVitals((metric) => {
  // Use `window.gtag` if you initialized Google Analytics as this example:
  // https://github.com/vercel/next.js/blob/canary/examples/with-google-analytics
  window.gtag('event', metric.name, {
    value: Math.round(
      metric.name === 'CLS' ? metric.value * 1000 : metric.value
    ), // values must be integers
    event_label: metric.id, // id unique to current page load
    non_interaction: true, // avoids affecting bounce rate.
  })
})

了解有关 将结果发送至 Google Analytics 的更多信息。

¥Read more about sending results to Google Analytics.