added orai

24_12_09/node_modules/web-vitals/dist/modules/onFCP.js

@@ -0,0 +1,71 @@
+/*
+ * 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.
+ */
+import { onBFCacheRestore } from './lib/bfcache.js';
+import { bindReporter } from './lib/bindReporter.js';
+import { doubleRAF } from './lib/doubleRAF.js';
+import { getActivationStart } from './lib/getActivationStart.js';
+import { getVisibilityWatcher } from './lib/getVisibilityWatcher.js';
+import { initMetric } from './lib/initMetric.js';
+import { observe } from './lib/observe.js';
+import { whenActivated } from './lib/whenActivated.js';
+/** Thresholds for FCP. See https://web.dev/articles/fcp#what_is_a_good_fcp_score */
+export const FCPThresholds = [1800, 3000];
+/**
+ * Calculates the [FCP](https://web.dev/articles/fcp) value for the current page and
+ * calls the `callback` function once the value is ready, along with the
+ * relevant `paint` performance entry used to determine the value. The reported
+ * value is a `DOMHighResTimeStamp`.
+ */
+export const onFCP = (onReport, opts) => {
+    // Set defaults
+    opts = opts || {};
+    whenActivated(() => {
+        const visibilityWatcher = getVisibilityWatcher();
+        let metric = initMetric('FCP');
+        let report;
+        const handleEntries = (entries) => {
+            entries.forEach((entry) => {
+                if (entry.name === 'first-contentful-paint') {
+                    po.disconnect();
+                    // Only report if the page wasn't hidden prior to the first paint.
+                    if (entry.startTime < visibilityWatcher.firstHiddenTime) {
+                        // The activationStart reference is used because FCP should be
+                        // relative to page activation rather than navigation start if the
+                        // page was prerendered. But in cases where `activationStart` occurs
+                        // after the FCP, this time should be clamped at 0.
+                        metric.value = Math.max(entry.startTime - getActivationStart(), 0);
+                        metric.entries.push(entry);
+                        report(true);
+                    }
+                }
+            });
+        };
+        const po = observe('paint', handleEntries);
+        if (po) {
+            report = bindReporter(onReport, metric, FCPThresholds, opts.reportAllChanges);
+            // Only report after a bfcache restore if the `PerformanceObserver`
+            // successfully registered or the `paint` entry exists.
+            onBFCacheRestore((event) => {
+                metric = initMetric('FCP');
+                report = bindReporter(onReport, metric, FCPThresholds, opts.reportAllChanges);
+                doubleRAF(() => {
+                    metric.value = performance.now() - event.timeStamp;
+                    report(true);
+                });
+            });
+        }
+    });
+};