small modifications

src/reportWebVitals.ts

@@ -1,15 +1,14 @@
 import { ReportHandler } from 'web-vitals';
 
-const reportWebVitals = (onPerfEntry?: ReportHandler) => {
-  if (onPerfEntry && onPerfEntry instanceof Function) {
-    import('web-vitals').then(({ getCLS, getFID, getFCP, getLCP, getTTFB }) => {
-      getCLS(onPerfEntry);  
-      getFID(onPerfEntry);
-      getFCP(onPerfEntry);
-      getLCP(onPerfEntry);
-      getTTFB(onPerfEntry);
-    });
-  }
-}
+export default function reportWebVitals(onPerfEntry?: ReportHandler) {
+  if (!onPerfEntry)
+    return;
 
-export default reportWebVitals;
+  import('web-vitals').then(({ getCLS, getFID, getFCP, getLCP, getTTFB }) => {
+    getCLS(onPerfEntry);
+    getFID(onPerfEntry);
+    getFCP(onPerfEntry);
+    getLCP(onPerfEntry);
+    getTTFB(onPerfEntry);
+  });
+}

src/setupTests.ts

@@ -1,5 +1 @@
-// jest-dom adds custom jest matchers for asserting on DOM nodes.
-// allows you to do things like:
-// expect(element).toHaveTextContent(/react/i)
-// learn more: https://github.com/testing-library/jest-dom
 import '@testing-library/jest-dom';

tsconfig.json

@@ -21,7 +21,7 @@
     "sourceMap": true,
     "declaration": true,
     "noUnusedLocals": true,
-    "noUnusedParameters": true,
+//    "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,
     "incremental": true
   },