Add Analytics

Google Analytics 4 Setup Skill

You are setting up Google Analytics 4 (GA4) for a project. Follow this comprehensive guide to add analytics properly.

Arguments

Parse the following from $ARGUMENTS:

Step 1: Detect Project Type

Scan the project to determine the framework/setup:

Priority detection order:
1. next.config.js/ts → Next.js
2. nuxt.config.js/ts → Nuxt.js
3. astro.config.mjs → Astro
4. svelte.config.js → SvelteKit
5. remix.config.js → Remix
6. gatsby-config.js → Gatsby
7. vite.config.js + src/App.vue → Vue + Vite
8. vite.config.js + src/App.tsx → React + Vite
9. angular.json → Angular
10. package.json with "react-scripts" → Create React App
11. index.html only → Plain HTML
12. _app.tsx/jsx → Next.js (App Router check: app/ directory)

Also check for:

Step 2: Validate Measurement ID

The Measurement ID must:

If the user provides a UA- ID, inform them: > "You provided a Universal Analytics ID (UA-). GA4 uses Measurement IDs starting with 'G-'. > Universal Analytics was sunset in July 2024. You'll need to create a GA4 property at analytics.google.com"

Step 3: Implementation by Framework

Next.js (App Router - app/ directory)

Create app/layout.tsx modification or create components/GoogleAnalytics.tsx:

// components/GoogleAnalytics.tsx
'use client'
import Script from 'next/script'
interface GoogleAnalyticsProps {
  measurementId: string
}
export function GoogleAnalytics({ measurementId }: GoogleAnalyticsProps) {
  return (
    <>
      
    
  )
}

Add to root layout:

// app/layout.tsx
import { GoogleAnalytics } from '@/components/GoogleAnalytics'
// Add inside  or :

Next.js (Pages Router - pages/ directory)

Modify pages/_app.tsx:

// pages/_app.tsx
import type { AppProps } from 'next/app'
import Script from 'next/script'
const GA_MEASUREMENT_ID = process.env.NEXT_PUBLIC_GA_MEASUREMENT_ID
export default function App({ Component, pageProps }: AppProps) {
  return (
    <>
      
      
    
  )
}

React (Vite/CRA)

Create src/lib/analytics.ts:

// src/lib/analytics.ts
export const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID
declare global {
  interface Window {
    gtag: (...args: unknown[]) => void
    dataLayer: unknown[]
  }
}
export const initGA = () => {
  if (typeof window === 'undefined') return
  const script = document.createElement('script')
  script.src = https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}
  script.async = true
  document.head.appendChild(script)
  window.dataLayer = window.dataLayer || []
  window.gtag = function gtag() {
    window.dataLayer.push(arguments)
  }
  window.gtag('js', new Date())
  window.gtag('config', GA_MEASUREMENT_ID)
}
export const pageview = (url: string) => {
  window.gtag('config', GA_MEASUREMENT_ID, {
    page_path: url,
  })
}
export const event = (action: string, params?: Record) => {
  window.gtag('event', action, params)
}

Initialize in src/main.tsx:

import { initGA } from './lib/analytics'
// Initialize before render
if (import.meta.env.PROD) {
  initGA()
}

Vue 3 (Vite)

Create src/plugins/analytics.ts:

// src/plugins/analytics.ts
import type { App } from 'vue'
import type { Router } from 'vue-router'
const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID
declare global {
  interface Window {
    gtag: (...args: unknown[]) => void
    dataLayer: unknown[]
  }
}
export const analyticsPlugin = {
  install(app: App, { router }: { router: Router }) {
    // Load gtag script
    const script = document.createElement('script')
    script.src = https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}
    script.async = true
    document.head.appendChild(script)
    window.dataLayer = window.dataLayer || []
    window.gtag = function gtag() {
      window.dataLayer.push(arguments)
    }
    window.gtag('js', new Date())
    window.gtag('config', GA_MEASUREMENT_ID)
    // Track route changes
    router.afterEach((to) => {
      window.gtag('config', GA_MEASUREMENT_ID, {
        page_path: to.fullPath,
      })
    })
    // Provide global methods
    app.config.globalProperties.$gtag = window.gtag
  }
}

Nuxt 3

Create plugins/analytics.client.ts:

// plugins/analytics.client.ts
export default defineNuxtPlugin(() => {
  const config = useRuntimeConfig()
  const measurementId = config.public.gaMeasurementId
  if (!measurementId) return
  // Load gtag
  useHead({
    script: [
      {
        src: https://www.googletagmanager.com/gtag/js?id=${measurementId},
        async: true,
      },
      {
        innerHTML: 
          window.dataLayer = window.dataLayer || [];
          function gtag(){dataLayer.push(arguments);}
          gtag('js', new Date());
          gtag('config', '${measurementId}');
        ,
      },
    ],
  })
  // Track route changes
  const router = useRouter()
  router.afterEach((to) => {
    window.gtag('config', measurementId, {
      page_path: to.fullPath,
    })
  })
})

Add to nuxt.config.ts:

export default defineNuxtConfig({
  runtimeConfig: {
    public: {
      gaMeasurementId: process.env.NUXT_PUBLIC_GA_MEASUREMENT_ID,
    },
  },
})

Astro

Create src/components/Analytics.astro:

---
// src/components/Analytics.astro
interface Props {
  measurementId: string
}
const { measurementId } = Astro.props

Add to layout:

---
import Analytics from '../components/Analytics.astro'


  
    
  

SvelteKit

Create src/lib/analytics.ts and src/routes/+layout.svelte:

// src/lib/analytics.ts
import { browser } from '$app/environment'
export const GA_MEASUREMENT_ID = import.meta.env.VITE_GA_MEASUREMENT_ID
export function initGA() {
  if (!browser) return
  const script = document.createElement('script')
  script.src = https://www.googletagmanager.com/gtag/js?id=${GA_MEASUREMENT_ID}
  script.async = true
  document.head.appendChild(script)
  window.dataLayer = window.dataLayer || []
  window.gtag = function gtag() {
    window.dataLayer.push(arguments)
  }
  window.gtag('js', new Date())
  window.gtag('config', GA_MEASUREMENT_ID)
}
export function trackPageview(url: string) {
  if (!browser) return
  window.gtag('config', GA_MEASUREMENT_ID, { page_path: url })
}

Plain HTML

Add to :

Step 4: Environment Variables

Create or update .env / .env.local:

# For Next.js
NEXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX
For Vite (React/Vue/Svelte)
VITE_GA_MEASUREMENT_ID=G-XXXXXXXXXX
For Nuxt
NUXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX

Add to .env.example if it exists (without the actual ID):

# Google Analytics 4 Measurement ID
NEXT_PUBLIC_GA_MEASUREMENT_ID=G-XXXXXXXXXX

IMPORTANT: Add .env.local to .gitignore if not already present.

Step 5: Event Tracking Helpers (if --events flag)

Create a comprehensive events utility:

// lib/analytics-events.ts
/**
 * GA4 Event Tracking Utilities
 *
 * Recommended events: https://support.google.com/analytics/answer/9267735
 */
type GTagEvent = {
  action: string
  category?: string
  label?: string
  value?: number
  [key: string]: unknown
}
// Core event function
export const trackEvent = ({ action, category, label, value, ...rest }: GTagEvent) => {
  if (typeof window === 'undefined' || !window.gtag) return
  window.gtag('event', action, {
    event_category: category,
    event_label: label,
    value,
    ...rest,
  })
}
// Engagement events
export const trackClick = (elementName: string, location?: string) => {
  trackEvent({
    action: 'click',
    category: 'engagement',
    label: elementName,
    click_location: location,
  })
}
export const trackScroll = (percentage: number) => {
  trackEvent({
    action: 'scroll',
    category: 'engagement',
    value: percentage,
  })
}
// Conversion events
export const trackSignUp = (method: string) => {
  trackEvent({
    action: 'sign_up',
    method,
  })
}
export const trackLogin = (method: string) => {
  trackEvent({
    action: 'login',
    method,
  })
}
export const trackPurchase = (params: {
  transactionId: string
  value: number
  currency: string
  items?: Array<{
    itemId: string
    itemName: string
    price: number
    quantity: number
  }>
}) => {
  trackEvent({
    action: 'purchase',
    transaction_id: params.transactionId,
    value: params.value,
    currency: params.currency,
    items: params.items,
  })
}
// Content events
export const trackSearch = (searchTerm: string) => {
  trackEvent({
    action: 'search',
    search_term: searchTerm,
  })
}
export const trackShare = (method: string, contentType: string, itemId: string) => {
  trackEvent({
    action: 'share',
    method,
    content_type: contentType,
    item_id: itemId,
  })
}
// Form events
export const trackFormStart = (formName: string) => {
  trackEvent({
    action: 'form_start',
    form_name: formName,
  })
}
export const trackFormSubmit = (formName: string, success: boolean) => {
  trackEvent({
    action: 'form_submit',
    form_name: formName,
    success,
  })
}
// Error tracking
export const trackError = (errorMessage: string, errorLocation?: string) => {
  trackEvent({
    action: 'exception',
    description: errorMessage,
    fatal: false,
    error_location: errorLocation,
  })
}
// Custom event builder for flexibility
export const createCustomEvent = (eventName: string) => {
  return (params?: Record) => {
    trackEvent({
      action: eventName,
      ...params,
    })
  }
}

Step 6: Cookie Consent Integration (if --consent flag)

Create a consent-aware wrapper:

// lib/analytics-consent.ts
type ConsentState = 'granted' | 'denied'
interface ConsentConfig {
  analytics_storage: ConsentState
  ad_storage: ConsentState
  ad_user_data: ConsentState
  ad_personalization: ConsentState
}
const CONSENT_COOKIE = 'analytics_consent'
// Initialize with consent mode
export const initWithConsent = (measurementId: string) => {
  if (typeof window === 'undefined') return
  // Set default consent state (denied until user consents)
  window.gtag('consent', 'default', {
    analytics_storage: 'denied',
    ad_storage: 'denied',
    ad_user_data: 'denied',
    ad_personalization: 'denied',
    wait_for_update: 500, // Wait for consent banner
  })
  // Load gtag
  const script = document.createElement('script')
  script.src = https://www.googletagmanager.com/gtag/js?id=${measurementId}
  script.async = true
  document.head.appendChild(script)
  window.dataLayer = window.dataLayer || []
  window.gtag = function gtag() {
    window.dataLayer.push(arguments)
  }
  window.gtag('js', new Date())
  window.gtag('config', measurementId)
  // Check for existing consent
  const savedConsent = getCookie(CONSENT_COOKIE)
  if (savedConsent) {
    updateConsent(JSON.parse(savedConsent))
  }
}
// Update consent when user makes a choice
export const updateConsent = (consent: Partial) => {
  if (typeof window === 'undefined' || !window.gtag) return
  const consentState: ConsentConfig = {
    analytics_storage: consent.analytics_storage || 'denied',
    ad_storage: consent.ad_storage || 'denied',
    ad_user_data: consent.ad_user_data || 'denied',
    ad_personalization: consent.ad_personalization || 'denied',
  }
  window.gtag('consent', 'update', consentState)
  // Save to cookie
  setCookie(CONSENT_COOKIE, JSON.stringify(consentState), 365)
}
// Convenience functions
export const acceptAll = () => {
  updateConsent({
    analytics_storage: 'granted',
    ad_storage: 'granted',
    ad_user_data: 'granted',
    ad_personalization: 'granted',
  })
}
export const acceptAnalyticsOnly = () => {
  updateConsent({
    analytics_storage: 'granted',
    ad_storage: 'denied',
    ad_user_data: 'denied',
    ad_personalization: 'denied',
  })
}
export const denyAll = () => {
  updateConsent({
    analytics_storage: 'denied',
    ad_storage: 'denied',
    ad_user_data: 'denied',
    ad_personalization: 'denied',
  })
}
// Cookie utilities
function setCookie(name: string, value: string, days: number) {
  const date = new Date()
  date.setTime(date.getTime() + days * 24 * 60 * 60 * 1000)
  document.cookie = ${name}=${value};expires=${date.toUTCString()};path=/;SameSite=Lax
}
function getCookie(name: string): string | null {
  const match = document.cookie.match(new RegExp((^| )${name}=([^;]+)))
  return match ? match[2] : null
}

Step 7: Debug Mode (if --debug flag)

Add debug configuration:

// For development, enable debug mode
if (process.env.NODE_ENV === 'development') {
  window.gtag('config', 'G-XXXXXXXXXX', {
    debug_mode: true,
  })
}

Also recommend installing the Google Analytics Debugger Chrome extension.

Step 8: TypeScript Declarations

Create types/gtag.d.ts if using TypeScript:

// types/gtag.d.ts
declare global {
  interface Window {
    gtag: Gtag.Gtag
    dataLayer: object[]
  }
}
declare namespace Gtag {
  interface Gtag {
    (command: 'config', targetId: string, config?: ConfigParams): void
    (command: 'set', targetId: string, config: ConfigParams): void
    (command: 'set', config: ConfigParams): void
    (command: 'js', date: Date): void
    (command: 'event', eventName: string, eventParams?: EventParams): void
    (command: 'consent', consentArg: 'default' | 'update', consentParams: ConsentParams): void
    (...args: unknown[]): void
  }
  interface ConfigParams {
    page_title?: string
    page_location?: string
    page_path?: string
    send_page_view?: boolean
    debug_mode?: boolean
    [key: string]: unknown
  }
  interface EventParams {
    event_category?: string
    event_label?: string
    value?: number
    [key: string]: unknown
  }
  interface ConsentParams {
    analytics_storage?: 'granted' | 'denied'
    ad_storage?: 'granted' | 'denied'
    ad_user_data?: 'granted' | 'denied'
    ad_personalization?: 'granted' | 'denied'
    wait_for_update?: number
  }
}
export {}

Step 9: Verification Checklist

After implementation, verify:

1. [ ] Measurement ID is correct format (G-XXXXXXXXXX) 2. [ ] Script loads in production (check Network tab) 3. [ ] Real-time reports show activity in GA4 dashboard 4. [ ] Page views are tracked on navigation 5. [ ] No console errors related to gtag 6. [ ] Environment variables are not committed to git 7. [ ] TypeScript has no type errors (if applicable)

Step 10: Summary Output

After completing setup, provide the user with:

1. Files created/modified (list them) 2. Environment variables needed (with example values) 3. Next steps: - Add the Measurement ID to environment variables - Deploy and verify in GA4 Real-time reports - Set up conversions in GA4 dashboard - Consider adding custom events for key user actions

Common Issues & Solutions

"gtag is not defined"

No data in GA4

Double page views

GDPR Compliance