Error Tracking & Elimination

Why Error Tracking Matters

The most immediate value of analytics for developers is finding errors that users never report. Most users who encounter a broken page simply leave — they do not file a bug report. Interestingly, the marketing of all things means we adopt a specialized term for this use of analytics to see how software is behaving: observability.

Server-Side Error Detection

Server access logs contain HTTP status codes for every request. Filter for 4xx (client errors: broken links, missing resources) and 5xx (server errors: crashes, timeouts). This requires no code changes — just log analysis.

Client-Side Error Detection

JavaScript errors, failed resource loads, and unhandled promise rejections are invisible to the server unless you explicitly capture and report them:

// Capture JavaScript errors window.addEventListener('error', function(event) { const errorData = { type: 'js_error', message: event.message, source: event.filename, line: event.lineno, column: event.colno, timestamp: Date.now(), url: location.href, userAgent: navigator.userAgent }; // sendBeacon guarantees delivery even during page unload navigator.sendBeacon('/collect', JSON.stringify(errorData)); }); // Capture unhandled promise rejections window.addEventListener('unhandledrejection', function(event) { navigator.sendBeacon('/collect', JSON.stringify({ type: 'promise_rejection', reason: String(event.reason), timestamp: Date.now(), url: location.href })); });