Initial Commit

node_modules/web-vitals/dist/modules/lib/observe.js

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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.
+ */
+/**
+ * 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 = (type, callback, opts) => {
+    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());
+                });
+            });
+            po.observe(Object.assign({
+                type,
+                buffered: true,
+            }, opts || {}));
+            return po;
+        }
+    }
+    catch (e) {
+        // Do nothing.
+    }
+    return;
+};