Initial Commit

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

@@ -0,0 +1,76 @@
+/*
+ * 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 { onTTFB as unattributedOnTTFB } from '../onTTFB.js';
+const attributeTTFB = (metric) => {
+    // Use a default object if no other attribution has been set.
+    let attribution = {
+        waitingDuration: 0,
+        cacheDuration: 0,
+        dnsDuration: 0,
+        connectionDuration: 0,
+        requestDuration: 0,
+    };
+    if (metric.entries.length) {
+        const navigationEntry = metric.entries[0];
+        const activationStart = navigationEntry.activationStart || 0;
+        // Measure from workerStart or fetchStart so any service worker startup
+        // time is included in cacheDuration (which also includes other sw time
+        // anyway, that cannot be accurately split out cross-browser).
+        const waitEnd = Math.max((navigationEntry.workerStart || navigationEntry.fetchStart) -
+            activationStart, 0);
+        const dnsStart = Math.max(navigationEntry.domainLookupStart - activationStart, 0);
+        const connectStart = Math.max(navigationEntry.connectStart - activationStart, 0);
+        const connectEnd = Math.max(navigationEntry.connectEnd - activationStart, 0);
+        attribution = {
+            waitingDuration: waitEnd,
+            cacheDuration: dnsStart - waitEnd,
+            // dnsEnd usually equals connectStart but use connectStart over dnsEnd
+            // for dnsDuration in case there ever is a gap.
+            dnsDuration: connectStart - dnsStart,
+            connectionDuration: connectEnd - connectStart,
+            // There is often a gap between connectEnd and requestStart. Attribute
+            // that to requestDuration so connectionDuration remains 0 for
+            // service worker controlled requests were connectStart and connectEnd
+            // are the same.
+            requestDuration: metric.value - connectEnd,
+            navigationEntry: navigationEntry,
+        };
+    }
+    // Use Object.assign to set property to keep tsc happy.
+    const metricWithAttribution = Object.assign(metric, { attribution });
+    return metricWithAttribution;
+};
+/**
+ * Calculates the [TTFB](https://web.dev/articles/ttfb) value for the
+ * current page and calls the `callback` function once the page has loaded,
+ * along with the relevant `navigation` performance entry used to determine the
+ * value. The reported value is a `DOMHighResTimeStamp`.
+ *
+ * Note, this function waits until after the page is loaded to call `callback`
+ * in order to ensure all properties of the `navigation` entry are populated.
+ * This is useful if you want to report on other metrics exposed by the
+ * [Navigation Timing API](https://w3c.github.io/navigation-timing/). For
+ * example, the TTFB metric starts from the page's [time
+ * origin](https://www.w3.org/TR/hr-time-2/#sec-time-origin), which means it
+ * includes time spent on DNS lookup, connection negotiation, network latency,
+ * and server processing time.
+ */
+export const onTTFB = (onReport, opts) => {
+    unattributedOnTTFB((metric) => {
+        const metricWithAttribution = attributeTTFB(metric);
+        onReport(metricWithAttribution);
+    }, opts);
+};