From 4507201ca22d9efddf35413edd8457b231f36fde Mon Sep 17 00:00:00 2001
From: Ioanna Kyprianou <51630004+ioanna0@users.noreply.github.com>
Date: Tue, 9 Mar 2021 20:06:09 +0200
Subject: [PATCH] fix: call mark if performance API exists (#193)

---
 src/EventTimer.ts | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/EventTimer.ts b/src/EventTimer.ts
index eedeb3ded..cc5ec8f86 100644
--- a/src/EventTimer.ts
+++ b/src/EventTimer.ts
@@ -106,18 +106,21 @@ export class EventTimer {
 		};
 	}
 
-	mark(name: string): PerformanceEntry {
+	mark(name: string): void {
 		const longName = `gu.commercial.${name}`;
-		window.performance.mark(longName);
-
-		// Most recent mark with this name is the event we just created.
-		const mark = window.performance
-			.getEntriesByName(longName, 'mark')
-			.slice(-1)[0];
-		if (typeof mark !== 'undefined') {
-			this.events.push(new Event(name, mark));
+		if (
+			typeof window.performance !== 'undefined' &&
+			'mark' in window.performance
+		) {
+			window.performance.mark(longName);
+			// Most recent mark with this name is the event we just created.
+			const mark = window.performance
+				.getEntriesByName(longName, 'mark')
+				.slice(-1)[0];
+			if (typeof mark !== 'undefined') {
+				this.events.push(new Event(name, mark));
+			}
 		}
-		return mark;
 	}
 
 	/**