Error sessions analysis with JavaScript errors

Error Sessions Analysis (JavaScript Errors)

Error sessions are user sessions with one or more JavaScript errors. JS errors break interface functionality, block forms and checkout, directly reducing conversion.

JavaScript Error Capture Setup

// Capture unhandled errors
window.addEventListener('error', function(event) {
  const errorInfo = {
    message: event.message,
    source: event.filename?.split('/').pop(),
    line: event.lineno,
    col: event.colno,
    stack: event.error?.stack?.slice(0, 500),
    page: window.location.pathname,
    user_agent: navigator.userAgent.slice(0, 100)
  }

  // Send to GA4
  gtag('event', 'js_error', errorInfo)

  // Send to Sentry/Bugsnag
  Sentry.captureException(event.error, {
    extra: errorInfo
  })
})

// Capture unhandled Promise rejections
window.addEventListener('unhandledrejection', function(event) {
  gtag('event', 'promise_rejection', {
    message: event.reason?.message || String(event.reason),
    page: window.location.pathname
  })
})

// Capture fetch/XHR errors
const originalFetch = window.fetch
window.fetch = async function(...args) {
  try {
    const response = await originalFetch(...args)
    if (!response.ok) {
      gtag('event', 'fetch_error', {
        url: args[0].toString().split('?')[0],
        status: response.status,
        page: window.location.pathname
      })
    }
    return response
  } catch (err) {
    gtag('event', 'fetch_exception', {
      url: args[0].toString().split('?')[0],
      message: err.message
    })
    throw err
  }
}

Sentry: Full Error Tracking

// sentry.init.js
import * as Sentry from '@sentry/browser'
import { BrowserTracing } from '@sentry/tracing'

Sentry.init({
  dsn: 'https://[email protected]/yyy',
  integrations: [
    new BrowserTracing(),
    new Sentry.Replay({
      maskAllText: false,
      blockAllMedia: false
    })
  ],
  tracesSampleRate: 0.1,   // 10% for performance
  replaysSessionSampleRate: 0.05,  // 5% of sessions
  replaysOnErrorSampleRate: 1.0,   // 100% on error
})

Analyzing Error Impact

Compare conversion rates for sessions with/without errors:

• Sessions with errors typically have 30-50% lower conversion
• Checkout errors have highest impact on revenue
• Navigation/menu errors reduce time on site

Delivery Time

Setting up error capture and analysis — 1 business day.