Tracking pageviews in single-page apps (SPA)

Jun 11, 2024

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A single-page application (or SPA) dynamically loads content for new pages using JavaScript instead of loading new pages from the server. Ideally, this enables users to navigate around the app without waiting for new pages to load, providing a seamless user experience.

PostHog's JavaScript Web SDK automatically captures pageview events on page load. The problem with SPAs is that page loads don't happen beyond the initial one. This means user navigation in your SPA isn't tracked.

To fix this, you can implement pageview capture manually using custom events. This tutorial shows you how to do this for the most popular SPA frameworks like Next.js, Vue, Svelte, and Angular.

Prerequisite: Each of these requires you to have an app created and PostHog installed. To install the PostHog JavaScript Web SDK, run the following command for the package manager of your choice:

Terminal
yarn add posthog-js
# or
npm install --save posthog-js
# or
pnpm add posthog-js

Tracking pageviews in Next.js (app router)

To add PostHog to your Next.js app, we start by creating the PostHogProvider component in the app folder. We set capture_pageview: false because we will manually capture pageviews.

JavaScript
// app/providers.js
'use client'
import posthog from 'posthog-js'
import { PostHogProvider } from 'posthog-js/react'


if (typeof window !== 'undefined') {
  posthog.init('<ph_project_api_key>', {
    api_host: 'https://us.i.posthog.com',
    person_profiles: 'identified_only',
    capture_pageview: false
  })
}


export function PHProvider({ children }) {
  return <PostHogProvider client={posthog}>{children}</PostHogProvider>
}

To capture pageviews, we create another pageview.js component in the app folder.

JavaScript
// app/pageview.js
'use client'


import { usePathname, useSearchParams } from "next/navigation";
import { useEffect } from "react";
import { usePostHog } from 'posthog-js/react';


export default function PostHogPageView() {
  const pathname = usePathname();
  const searchParams = useSearchParams();
  const posthog = usePostHog();
  // Track pageviews
  useEffect(() => {
    if (pathname && posthog) {
      let url = window.origin + pathname
      if (searchParams.toString()) {
        url = url + `?${searchParams.toString()}`
      }
      posthog.capture(
        '$pageview',
        {
          '$current_url': url,
        }
      )
    }
  }, [pathname, searchParams, posthog])
  
  return null
}

Finally, we import both and put them together in the app/layout.js file.

JavaScript
// app/layout.js
import "./globals.css";
import { PHProvider } from './providers'
import dynamic from 'next/dynamic'


const PostHogPageView = dynamic(() => import('./pageview'), {
  ssr: false,
})


export default function RootLayout({ children }) {
  return (
    <html lang="en">
      <PHProvider>
        <body>
          {children}
          <PostHogPageView />
        </body>
      </PHProvider>
    </html>
  );
}

Make sure to dynamically import the PostHogPageView component or the useSearchParams hook will deopt the entire app into client-side rendering.

Tracking pageviews in Vue

After creating a Vue app and setting up the vue-router, create a new folder in the src/components named plugins. In this folder, create a file named posthog.js. This is where we initialize PostHog.

JavaScript
// src/plugins/posthog.js
import posthog from "posthog-js";


export default {
  install(app) {
    app.config.globalProperties.$posthog = posthog.init(
      "<ph_project_api_key>",
      {
        api_host: "https://us.i.posthog.com",
        person_profiles: 'identified_only',
        capture_pageview: false
      }
    );
  },
};

After this, you can add the plugin to the main.js file and use it along with the router to capture pageviews afterEach route change.

JavaScript
// src/main.js
import { createApp, nextTick } from 'vue'
import App from './App.vue'
import router from './router'
import posthogPlugin from '../plugins/posthog';


const app = createApp(App);
app.use(posthogPlugin).use(router).mount('#app');


router.afterEach((to, from, failure) => {
  if (!failure) {
    nextTick(() => {
      app.config.globalProperties.$posthog.capture(
        '$pageview', 
        { path: to.fullPath }
      );
    });
  }
});

Tracking pageviews in Svelte

If you haven't already, start by creating a +layout.js file for your Svelte app in your src/routes folder. In it, add the code to initialize PostHog.

JavaScript
// src/routes/+layout.js
import posthog from 'posthog-js'
import { browser } from '$app/environment';


export const load = async () => {


  if (browser) {
    posthog.init(
      '<ph_project_api_key>',
      {
        api_host: 'https://us.i.posthog.com',
        person_profiles: 'identified_only',
        capture_pageview: false
      }
    )
  }
  return
};

After that, create a +layout.svelte file in src/routes. In it, use the afterNavigate interceptor to capture pageviews.

Svelte
<!-- src/routes/+layout.svelte -->
<script>
  import posthog from 'posthog-js'
  import { browser } from '$app/environment';
  import { beforeNavigate, afterNavigate } from '$app/navigation';


  if (browser) {
    afterNavigate(() => posthog.capture('$pageview'));
  }
</script>


<slot></slot>

Tracking pageviews in Angular

To start tracking pageviews in Angular, begin by initializing PostHog in src/main.ts.

JavaScript
import { bootstrapApplication } from '@angular/platform-browser';
import { appConfig } from './app/app.config';
import { AppComponent } from './app/app.component';
import posthog from 'posthog-js';


posthog.init('<ph_project_api_key>',
  {
    api_host: 'https://us.i.posthog.com',
    person_profiles: 'identified_only',
    capture_pageview: false
  }
);


bootstrapApplication(AppComponent, appConfig)
  .catch((err) => console.error(err));

After setting up your routes and router, you can capture pageviews by subscribing to navigationEnd events in app.component.ts.

JavaScript
import { Component } from '@angular/core';
import { RouterOutlet, Router, Event, NavigationEnd } from '@angular/router';
import { filter } from 'rxjs/operators';
import { Observable } from 'rxjs';
import posthog from 'posthog-js';


@Component({
  selector: 'app-root',
  standalone: true,
  imports: [RouterOutlet],
  templateUrl: './app.component.html',
  styleUrl: './app.component.css'
})
export class AppComponent {
  title = 'angular-spa';
  navigationEnd: Observable<NavigationEnd>;


  constructor(public router: Router) {
    this.navigationEnd = router.events.pipe(
      filter((event: Event) => event instanceof NavigationEnd)
    ) as Observable<NavigationEnd>;
  }


  ngOnInit() {
    this.navigationEnd.subscribe((event: NavigationEnd) => {
      posthog.capture('$pageview');
    });
  }
}

Further reading