Added guardian for browser support of PerformanceLongTaskTiming 🐿 v2.…

…12.5
Financial-Times · Dec 31, 2019 · 4c49b5f · 4c49b5f
1 parent 93c15af
commit 4c49b5f
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/src/client/trackers/real-user-monitoring-for-performance.js b/src/client/trackers/real-user-monitoring-for-performance.js
@@ -24,7 +24,14 @@ const requiredMetrics = [
 ];
 
 const cohortPercent = 5;
+
 export const realUserMonitoringForPerformance = () => {
+
+	// Check browser support.
+	// @see https://developer.mozilla.org/en-US/docs/Web/API/PerformanceLongTaskTiming
+	if (!'PerformanceLongTaskTiming' in window) return;
+
+	// Gather metrics for only a cohort of users.
 	if (!userIsInCohort(cohortPercent)) return;
 
 	const navigation = performance.getEntriesByType('navigation')[0];