simplified special cases handling in resolveByPath

sitemap-parser/src/resolveByPath.ts

@@ -16,26 +16,22 @@ import { Sitemap } from './types';
         );
     };*/
 
-const createPaths = (
-    sitemap: Sitemap | null | undefined,
-): [string, number][] =>
-    !sitemap
-        ? []
-        : sitemap.children.flatMap((childNode) => [
-              [childNode.name, childNode.id] as [string, number],
-              ...createPaths(childNode).map(
-                  ([path, id]) =>
-                      [`${childNode.name}/${path}`, id] as [string, number],
+const createPaths = (node: Sitemap): Readonly<[string, number]>[] => [
+    ['', node.id],
+    ...node.children.flatMap((childNode) =>
+        createPaths(childNode).map(
+            ([path, id]) => [`/${childNode.name}${path}`, id] as const,
         ),
-          ]);
+    ),
+];
 
 // Second, improved implementation, where we build a static hashmap from complete paths to IDs once,
 // and then use it as a single lookup table.
 export const createPathResolver = (sitemap: Sitemap | null) => {
-    const paths = new Map(
-        createPaths(sitemap).map(([path, id]) => [`/${path}`, id]),
+    const rawPathsData = sitemap ? createPaths(sitemap) : [];
+    const pathsMap = new Map(
+        rawPathsData.map(([path, id]) => [path.length ? path : '/', id]),
     );
 
-    return (path: string) =>
-        (path === '/' ? sitemap?.id : paths.get(path)) ?? null;
+    return (path: string) => pathsMap.get(path) ?? null;
 };