Apply suggestions from code review

Co-authored-by: Matt Cowley <[email protected]>

Author: flakey5

src/utils/request.ts

@@ -29,15 +29,18 @@ export function parseUrl(request: Request): URL | undefined {
   return url;
 }
 
+export function isValidDate(date?: Date): boolean {
+  return date instanceof Date && !isNaN(date);
+}
+
 export function parseConditionalHeaders(headers: Headers): ConditionalHeaders {
   let ifModifiedSince = headers.has('if-modified-since')
     ? new Date(headers.get('if-modified-since')!)
     : undefined;
 
-  if (ifModifiedSince instanceof Date) {
+  if (isValidDate(ifModifiedSince)) {
     ifModifiedSince.setSeconds(ifModifiedSince.getSeconds() + 1);
   } else {
-    // Invalid date
     ifModifiedSince = undefined;
   }
 
@@ -53,8 +56,7 @@ export function parseConditionalHeaders(headers: Headers): ConditionalHeaders {
     ? new Date(headers.get('if-unmodified-since')!)
     : undefined;
 
-  if (!(ifUnmodifiedSince instanceof Date)) {
-    // Invalid date
+  if (!isValidDate(ifUnmodifiedSince)) {
     ifUnmodifiedSince = undefined;
   }