Subchapter 190.3

Next Js

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Next.js - Docs

PostHog makes it easy to get data about traffic and usage of your Next.js app. Integrating PostHog into your site enables analytics about user behavior, custom events capture, session recordings, feature flags, and more.

Next Js · Feature Flags Next.js · PostHog/skills · Skills Docs

'use client'
import posthog from 'posthog-js'
export default function Home() {
  return (
    <div>
      <button onClick={() => posthog.capture('test_event')}>
        Click me for an event
      </button>
    </div>
  );
}

'use client'
import { useFeatureFlagEnabled } from 'posthog-js/react'
export default function FeatureComponent() {
  const showNewFeature = useFeatureFlagEnabled('new-feature')
  return showNewFeature ? <NewFeature /> : <OldFeature />
}

// app/posthog.js
import { PostHog } from 'posthog-node'
export default function PostHogClient() {
  const posthogClient = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_TOKEN, {
    host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
    flushAt: 1,
    flushInterval: 0
  })
  return posthogClient
}

import Link from 'next/link'
import PostHogClient from '../posthog'
export default async function About() {
  const posthog = PostHogClient()
  const flags = await posthog.getAllFlags(
    'user_distinct_id' // replace with a user's distinct ID
  );
  await posthog.shutdown()
  return (
    <main>
      <h1>About</h1>
      <Link href="/">Go home</Link>
      { flags['main-cta'] &&
        <Link href="http://posthog.com/">Go to PostHog</Link>
      }
    </main>
  )
}

// pages/posts/[id].js
import { useContext, useEffect, useState } from 'react'
import { getServerSession } from "next-auth/next"
import { PostHog } from 'posthog-node'
export default function Post({ post, flags }) {
  const [ctaState, setCtaState] = useState()
  useEffect(() => {
    if (flags) {
      setCtaState(flags['blog-cta'])
    }
  })
  return (
    <div>
      <h1>{post.title}</h1>
      <p>By: {post.author}</p>
      <p>{post.content}</p>
      {ctaState &&
        <p><a href="/">Go to PostHog</a></p>
      }
      <button onClick={likePost}>Like</button>
    </div>
  )
}
export async function getServerSideProps(ctx) {
  const session = await getServerSession(ctx.req, ctx.res)
  let flags = null
  if (session) {
    const client = new PostHog(
      process.env.NEXT_PUBLIC_POSTHOG_TOKEN,
      {
        host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
      }
    )
    flags = await client.getAllFlags(session.user.email);
    client.capture({
      distinctId: session.user.email,
      event: 'loaded blog article',
      properties: {
        $current_url: ctx.req.url,
      },
    });
    await client.shutdown()
  }
  const { posts } = await import('../../blog.json')
  const post = posts.find((post) => post.id.toString() === ctx.params.id)
  return {
    props: {
      post,
      flags
    },
  }
}

posthog.init(process.env.NEXT_PUBLIC_POSTHOG_TOKEN, {
  // ... your configuration
  fetch_options: {
    cache: 'force-cache', // Use Next.js cache
    next_options: {       // Passed to the `next` option for `fetch`
      revalidate: 60,     // Cache for 60 seconds
      tags: ['posthog'],  // Can be used with Next.js `revalidateTag` function
    },
  }
})

Next Js

Next.js - Docs

Next Js

Next.js - Docs

Prerequisites

Beta: integration via LLM

Client-side setup

npm

Yarn

pnpm

Bun

Integration

instrumentation-client.js

instrumentation-client.ts

Identifying users

Accessing PostHog

Using React hooks

Usage

Server-side analytics

npm

Yarn

pnpm

Bun

Router-specific instructions

App router

Pages router

Server-side configuration

Configuring a reverse proxy to PostHog

Further reading

Community questions

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