Update app and tooling

node_modules/web-vitals/src/getCLS.ts

@@ -0,0 +1,57 @@
+/*
+ * 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 {initMetric} from './lib/initMetric.js';
+import {observe, PerformanceEntryHandler} from './lib/observe.js';
+import {onHidden} from './lib/onHidden.js';
+import {bindReporter} from './lib/bindReporter.js';
+import {ReportHandler} from './types.js';
+
+
+// https://wicg.github.io/layout-instability/#sec-layout-shift
+interface LayoutShift extends PerformanceEntry {
+  value: number;
+  hadRecentInput: boolean;
+}
+
+export const getCLS = (onReport: ReportHandler, reportAllChanges = false) => {
+  const metric = initMetric('CLS', 0);
+
+  let report: ReturnType<typeof bindReporter>;
+
+  const entryHandler = (entry: LayoutShift) => {
+    // Only count layout shifts without recent user input.
+    if (!entry.hadRecentInput) {
+      (metric.value as number) += entry.value;
+      metric.entries.push(entry);
+      report();
+    }
+  };
+
+  const po = observe('layout-shift', entryHandler as PerformanceEntryHandler);
+  if (po) {
+    report = bindReporter(onReport, metric, po, reportAllChanges);
+
+    onHidden(({isUnloading}) => {
+      po.takeRecords().map(entryHandler as PerformanceEntryHandler);
+
+      if (isUnloading) {
+        metric.isFinal = true;
+      }
+      report();
+    });
+  }
+};