1 files changed, 66 insertions, 0 deletions
diff --git a/frontend-old/node_modules/web-vitals/src/lib/observe.ts b/frontend-old/node_modules/web-vitals/src/lib/observe.ts
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+++ b/frontend-old/node_modules/web-vitals/src/lib/observe.ts
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+/*
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+interface PerformanceEntryMap {
+  'event': PerformanceEventTiming[];
+  'first-input': PerformanceEventTiming[];
+  'layout-shift': LayoutShift[];
+  'largest-contentful-paint': LargestContentfulPaint[];
+  'long-animation-frame': PerformanceLongAnimationFrameTiming[];
+  'paint': PerformancePaintTiming[];
+  'navigation': PerformanceNavigationTiming[];
+  'resource': PerformanceResourceTiming[];
+}
+
+/**
+ * Takes a performance entry type and a callback function, and creates a
+ * `PerformanceObserver` instance that will observe the specified entry type
+ * with buffering enabled and call the callback _for each entry_.
+ *
+ * This function also feature-detects entry support and wraps the logic in a
+ * try/catch to avoid errors in unsupporting browsers.
+ */
+export const observe = <K extends keyof PerformanceEntryMap>(
+  type: K,
+  callback: (entries: PerformanceEntryMap[K]) => void,
+  opts?: PerformanceObserverInit,
+): PerformanceObserver | undefined => {
+  try {
+    if (PerformanceObserver.supportedEntryTypes.includes(type)) {
+      const po = new PerformanceObserver((list) => {
+        // Delay by a microtask to workaround a bug in Safari where the
+        // callback is invoked immediately, rather than in a separate task.
+        // See: https://github.com/GoogleChrome/web-vitals/issues/277
+        Promise.resolve().then(() => {
+          callback(list.getEntries() as PerformanceEntryMap[K]);
+        });
+      });
+      po.observe(
+        Object.assign(
+          {
+            type,
+            buffered: true,
+          },
+          opts || {},
+        ) as PerformanceObserverInit,
+      );
+      return po;
+    }
+  } catch (e) {
+    // Do nothing.
+  }
+  return;
+};