Not monitoring errors ("No user feedback means no problems")

Not Monitoring Errors ("No User Feedback Means No Problem")

The most dangerous illusion in front-end development is that "no errors reported equals no problems." User silence does not indicate system health—it could mean errors are being swallowed, users can't be bothered to provide feedback, or they simply don't know what counts as "abnormal." Code produced under this mindset is like a waterway riddled with hidden reefs: calm on the surface but fraught with peril beneath.

The Black Hole Pattern of Error Swallowing

The most common anti-pattern is actively catching errors but doing nothing with them, such as:

// Catastrophic approach: errors are completely swallowed
try {
  JSON.parse(userInput)
} catch (e) {
  // Black hole catch—nothing happens
}

// A slightly "gentler" variant
try {
  loadThirdPartyScript()
} catch {
  console.log('Third-party script failed to load') // Since when are console logs considered error handling?
}

A more insidious approach is disguising error handling as "friendly prompts":

function fetchUserData() {
  return axios.get('/api/user').catch(() => {
    return { status: 'failed' } // Masking errors with default values
  })
}

The Domino Effect of Silent Failures

Unhandled errors trigger a chain reaction of more hidden issues:

1. Data Corruption: A form submission fails, but the UI shows "success" while the data remains unsaved.
2. State Inconsistency: A shopping cart item fails to delete, but the UI updates anyway.
3. Avalanche Effect: One API failure leads to all subsequent requests using incorrect parameters.

// A classic data synchronization disaster
async function syncData() {
  const result = await saveData().catch(console.error) // Half-hearted handling
  if (result) { // This will always be true because failures return undefined
    updateUI() // Executes no matter what
  }
}

The Unreliability of User Feedback

Relying on user feedback as an error-monitoring mechanism is fatally flawed:

• The Silent Majority: 95% of users won’t proactively report issues.
• Cognitive Bias: Users might blame their own network for UI freezes.
• Reproduction Difficulty: Descriptions like "sometimes the button doesn’t work" are useless.

Experimental data shows:

• Unhandled Promise rejections occur in up to 12% of mobile sessions.
• ~40% of JS errors originate from third-party scripts.
• Users typically endure the same error 3 times before considering feedback.

Laziness Disguised as "Graceful Degradation"

Many developers justify unhandled errors with "graceful degradation":

function getGeoLocation() {
  return navigator.geolocation.getCurrentPosition(
    pos => pos,
    () => ({ lat: 0, lng: 0 }) // Pretending to return a default location
  )
}

This approach leads to:

• Maps displaying off the coast of Africa (coordinates 0,0).
• Delivery systems calculating absurd shipping fees.
• Analytics polluted with garbage data.

Building an Error Monitoring System

True defensive programming requires systematic monitoring:

1. Global Error Capture

// Front-end error monitoring foundation
window.addEventListener('error', (e) => {
  sentry.captureException(e)
  metrics.increment('client_error') 
})

window.addEventListener('unhandledrejection', (e) => {
  sentry.captureException(e.reason)
})

2. Critical Path Instrumentation

// Tagging critical operations
async function checkout() {
  const span = tracer.startSpan('checkout')
  try {
    await submitOrder()
  } catch (e) {
    span.setTag('error', true)
    throw e // Re-throw instead of swallowing
  } finally {
    span.finish()
  }
}

3. Automated Monitoring Dashboards

• Error rate overview (grouped by hour/version/device).
• Affected user count statistics.
• Error stack clustering analysis.

The Dark Art of Error Recovery

When errors are inevitable, at least ensure predictability:

// Payment retry mechanism example
async function retryPayment(times = 3) {
  for (let i = 0; i < times; i++) {
    try {
      return await pay()
    } catch (e) {
      if (e.code === 'TIMEOUT') continue
      if (e.code === 'BALANCE_NOT_ENOUGH') {
        showError('Insufficient balance') // Specific errors get clear prompts
        throw e
      }
    }
  }
  showError('Network unstable—please retry later')
}

Deceptive UX for Error Perception

Even when "swallowing" errors, make users aware of state changes:

// Fake loading state
let fakeLoading = false

async function submitForm() {
  fakeLoading = true
  try {
    await actualSubmit()
  } catch {
    // Secretly retry once
    await actualSubmit().catch(() => {
      showToast('Submission delayed—data will sync when network recovers')
      queueMicrotask(() => saveToIndexedDB(data))
    })
  } finally {
    fakeLoading = false
  }
}

The Production Error Carnival

Intentionally disabling all error monitoring in production:

// The most reckless configuration possible
if (process.env.NODE_ENV === 'production') {
  console.error = () => {}
  window.onerror = null
  Sentry.close()
}

The "benefits" of this approach:

• Zero alerts in monitoring = "Zero errors."
• User complaints become the sole KPI.
• Year-end reports can proudly claim "100% system stability."