Initial Commit

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

@@ -0,0 +1,83 @@
+/*
+ * 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 { getNavigationEntry } from '../lib/getNavigationEntry.js';
+import { getSelector } from '../lib/getSelector.js';
+import { onLCP as unattributedOnLCP } from '../onLCP.js';
+const attributeLCP = (metric) => {
+    // Use a default object if no other attribution has been set.
+    let attribution = {
+        timeToFirstByte: 0,
+        resourceLoadDelay: 0,
+        resourceLoadDuration: 0,
+        elementRenderDelay: metric.value,
+    };
+    if (metric.entries.length) {
+        const navigationEntry = getNavigationEntry();
+        if (navigationEntry) {
+            const activationStart = navigationEntry.activationStart || 0;
+            const lcpEntry = metric.entries[metric.entries.length - 1];
+            const lcpResourceEntry = lcpEntry.url &&
+                performance
+                    .getEntriesByType('resource')
+                    .filter((e) => e.name === lcpEntry.url)[0];
+            const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
+            const lcpRequestStart = Math.max(ttfb, 
+            // Prefer `requestStart` (if TOA is set), otherwise use `startTime`.
+            lcpResourceEntry
+                ? (lcpResourceEntry.requestStart || lcpResourceEntry.startTime) -
+                    activationStart
+                : 0);
+            const lcpResponseEnd = Math.max(lcpRequestStart, lcpResourceEntry ? lcpResourceEntry.responseEnd - activationStart : 0);
+            const lcpRenderTime = Math.max(lcpResponseEnd, lcpEntry.startTime - activationStart);
+            attribution = {
+                element: getSelector(lcpEntry.element),
+                timeToFirstByte: ttfb,
+                resourceLoadDelay: lcpRequestStart - ttfb,
+                resourceLoadDuration: lcpResponseEnd - lcpRequestStart,
+                elementRenderDelay: lcpRenderTime - lcpResponseEnd,
+                navigationEntry,
+                lcpEntry,
+            };
+            // Only attribution the URL and resource entry if they exist.
+            if (lcpEntry.url) {
+                attribution.url = lcpEntry.url;
+            }
+            if (lcpResourceEntry) {
+                attribution.lcpResourceEntry = lcpResourceEntry;
+            }
+        }
+    }
+    // Use Object.assign to set property to keep tsc happy.
+    const metricWithAttribution = Object.assign(metric, { attribution });
+    return metricWithAttribution;
+};
+/**
+ * Calculates the [LCP](https://web.dev/articles/lcp) value for the current page and
+ * calls the `callback` function once the value is ready (along with the
+ * relevant `largest-contentful-paint` performance entry used to determine the
+ * value). The reported value is a `DOMHighResTimeStamp`.
+ *
+ * If the `reportAllChanges` configuration option is set to `true`, the
+ * `callback` function will be called any time a new `largest-contentful-paint`
+ * performance entry is dispatched, or once the final value of the metric has
+ * been determined.
+ */
+export const onLCP = (onReport, opts) => {
+    unattributedOnLCP((metric) => {
+        const metricWithAttribution = attributeLCP(metric);
+        onReport(metricWithAttribution);
+    }, opts);
+};