Add time-on-page custom event

shared-code/time-on-page.js

@@ -0,0 +1,27 @@
+// NOTE: This implementation does not consider whether the page is in an active tab of the browser.
+// If you want to exclude time where the current tab is not active you can use the visibilitychange event to pause the timer.
+
+// TODO: Replace the value below with a unique event key for this experiment.
+// For example, 'checkout_time_on_page'.
+const eventName = 'example_time_on_page';
+
+// Capture the starting time
+const startDate = new Date();
+
+// Attach event listener
+window.addEventListener('beforeunload', () => {
+  const endDate = new Date();
+  const spentTime = (endDate.getTime() - startDate.getTime()) / 1000;
+
+  // Verify that Optimizely is on the page
+  if (window.optimizely) {
+    // Send event
+    window.optimizely.push({
+      type: 'event',
+      eventName,
+      tags: {
+        value: spentTime
+      }
+    });
+  }
+});