How to use google analytics with next.js app?

I'm using styled-components with next.js so my styles need to be server-side rendered, hence how can I add google analytics to my website?

I checked next.js google analytics example but as I said my _document file is different because of using styled-components.

// _document.js

import React from 'react'
import Document from 'next/document'
import { ServerStyleSheet } from 'styled-components'

class MyDocument extends Document {
  static async getInitialProps(ctx) {
    const sheet = new ServerStyleSheet()
    const originalRenderPage = ctx.renderPage

    try {
      ctx.renderPage = () => originalRenderPage({
        enhanceApp: (App) => (props) => sheet.collectStyles(<App {...props} />),
      })

      const initialProps = await Document.getInitialProps(ctx)
      return {
        ...initialProps,
        styles: (
          <>
            {initialProps.styles}
            {sheet.getStyleElement()}
          </>
        ),
      }
    } finally {
      sheet.seal()
    }
  }
}

export default MyDocument

To correctly initialize gtag, do the following in _document.js or wherever you defined Head:

import { Head } from 'next/document';

export default class MyDocument extends Document {
  render() {
    return (
      // ...
      <Head>
        <script
          async
          src="https://www.googletagmanager.com/gtag/js?id=[Tracking ID]"
        />

        <script
          dangerouslySetInnerHTML={{
            __html: `
              window.dataLayer = window.dataLayer || [];
              function gtag(){dataLayer.push(arguments);}
              gtag('js', new Date());
              gtag('config', '[Tracking ID]', { page_path: window.location.pathname });
            `,
          }}
        />
      </Head>
    );
  }
}

The above will track page views on page load. To track navigation add the following to _app.js:

import { useRouter } from 'next/router';
import { useEffect } from "react";

export default const App = () => {
  const router = useRouter();

  const handleRouteChange = (url) => {
    window.gtag('config', '[Tracking ID]', {
      page_path: url,
    });
  };

  useEffect(() => {
    router.events.on('routeChangeComplete', handleRouteChange);
    return () => {
      router.events.off('routeChangeComplete', handleRouteChange);
    };
  }, [router.events]);

  return (
    // ...
  );
};

To setup Google analytics with NextJS using Typescript

I'm using below setup for my personal site (https://github.com/GorvGoyl/Personal-Site-Gourav.io) and it's working fine without any linting errors. Analytics is enabled only for production.

Create a Google analytics project and get Measurement ID.
In your NextJS project, create /lib/gtag.ts file and add your Google Measurement ID:

export const GA_TRACKING_ID = "<INSERT_TAG_ID>";

// https://developers.google.com/analytics/devguides/collection/gtagjs/pages
export const pageview = (url: URL): void => {
  window.gtag("config", GA_TRACKING_ID, {
    page_path: url,
  });
};

type GTagEvent = {
  action: string;
  category: string;
  label: string;
  value: number;
};

// https://developers.google.com/analytics/devguides/collection/gtagjs/events
export const event = ({ action, category, label, value }: GTagEvent): void => {
  window.gtag("event", action, {
    event_category: category,
    event_label: label,
    value,
  });
};

Also install gtag types:

npm i -D @types/gtag.js

Create /pages/_document.tsx:

import Document, { Html, Head, Main, NextScript } from "next/document";

import { GA_TRACKING_ID } from "../lib/gtag";

const isProduction = process.env.NODE_ENV === "production";

export default class MyDocument extends Document {
  render(): JSX.Element {
    return (
      <Html>
        <Head>
          {/* enable analytics script only for production */}
          {isProduction && (
            <>
              <script
                async
                src={`https://www.googletagmanager.com/gtag/js?id=${GA_TRACKING_ID}`}
              />
              <script
                // eslint-disable-next-line react/no-danger
                dangerouslySetInnerHTML={{
                  __html: `
            window.dataLayer = window.dataLayer || [];
            function gtag(){dataLayer.push(arguments);}
            gtag('js', new Date());
            gtag('config', '${GA_TRACKING_ID}', {
              page_path: window.location.pathname,
            });
          `,
                }}
              />
            </>
          )}
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    );
  }
}

Create /pages/_app.tsx:

import { AppProps } from "next/app";
import { useRouter } from "next/router";
import { useEffect } from "react";
import * as gtag from "../lib/gtag";
const isProduction = process.env.NODE_ENV === "production";

const App = ({ Component, pageProps }: AppProps): JSX.Element => {
  const router = useRouter();

  useEffect(() => {
    const handleRouteChange = (url: URL) => {
      /* invoke analytics function only for production */
      if (isProduction) gtag.pageview(url);
    };
    router.events.on("routeChangeComplete", handleRouteChange);
    return () => {
      router.events.off("routeChangeComplete", handleRouteChange);
    };
  }, [router.events]);
  // eslint-disable-next-line react/jsx-props-no-spreading
  return <Component {...pageProps} />;
};

export default App;

More info: https://gourav.io/blog/nextjs-cheatsheet

In your _document.js you override the getInitialProps method. You can also override the render method. Simply add

  render() {
    return (
      <Html lang={this.props.lang || "en"}>
        <Head>
          <script
            dangerouslySetInnerHTML={{
              __html: `[google analytics tracking code here]`
            }}
          />
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    );
  }

Make sure you import the required components:

import Document, { Html, Head, Main, NextScript } from "next/document"

Another way that worked well to me without dangerouslySetInnerHTML:

Create a new js file in the public folder with the contents in dangerouslySetInnerHTML.
Add that created js file to the _document.js file.

The sample for what my _document.js returned:

<Html>
  <Head>
    <script async src="https://www.googletagmanager.com/gtag/js?id=UA-xxx-x"></script>
    <script src="/ga.js" async></script>
    {/*other scripts*/}
  </Head>
  <body>
    <Main />
      <NextScript />
  </body>
</Html>

How to use google analytics with next.js app?

To setup Google analytics with NextJS using Typescript

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