Initial Commit

node_modules/web-vitals/dist/modules/attribution/onFCP.js

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2022 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 { getBFCacheRestoreTime } from '../lib/bfcache.js';
+import { getLoadState } from '../lib/getLoadState.js';
+import { getNavigationEntry } from '../lib/getNavigationEntry.js';
+import { onFCP as unattributedOnFCP } from '../onFCP.js';
+const attributeFCP = (metric) => {
+    // Use a default object if no other attribution has been set.
+    let attribution = {
+        timeToFirstByte: 0,
+        firstByteToFCP: metric.value,
+        loadState: getLoadState(getBFCacheRestoreTime()),
+    };
+    if (metric.entries.length) {
+        const navigationEntry = getNavigationEntry();
+        const fcpEntry = metric.entries[metric.entries.length - 1];
+        if (navigationEntry) {
+            const activationStart = navigationEntry.activationStart || 0;
+            const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
+            attribution = {
+                timeToFirstByte: ttfb,
+                firstByteToFCP: metric.value - ttfb,
+                loadState: getLoadState(metric.entries[0].startTime),
+                navigationEntry,
+                fcpEntry,
+            };
+        }
+    }
+    // Use Object.assign to set property to keep tsc happy.
+    const metricWithAttribution = Object.assign(metric, { attribution });
+    return metricWithAttribution;
+};
+/**
+ * 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) => {
+    unattributedOnFCP((metric) => {
+        const metricWithAttribution = attributeFCP(metric);
+        onReport(metricWithAttribution);
+    }, opts);
+};