perf: compute mapping of folder name to file data for faster breadcrumbs

quartz/components/Breadcrumbs.tsx

@@ -41,25 +41,13 @@ function formatCrumb(displayName: string, baseSlug: FullSlug, currentSlug: Simpl
   }
 }
 
-// given a folderName (e.g. "features"), search for the corresponding `index.md` file
-function findCurrentFile(allFiles: QuartzPluginData[], folderName: string) {
-  return allFiles.find((file) => {
-    if (file.slug?.endsWith("index")) {
-      const folderParts = file.filePath?.split("/")
-      if (folderParts) {
-        const name = folderParts[folderParts?.length - 2]
-        if (name === folderName) {
-          return true
-        }
-      }
-    }
-  })
-}
-
 export default ((opts?: Partial<BreadcrumbOptions>) => {
   // Merge options with defaults
   const options: BreadcrumbOptions = { ...defaultOptions, ...opts }
 
+  // computed index of folder name to its associated file data
+  let folderIndex: Map<string, QuartzPluginData> | undefined
+
   function Breadcrumbs({ fileData, allFiles, displayClass }: QuartzComponentProps) {
     // Hide crumbs on root if enabled
     if (options.hideOnRoot && fileData.slug === "index") {
@@ -70,28 +58,39 @@ export default ((opts?: Partial<BreadcrumbOptions>) => {
     const firstEntry = formatCrumb(options.rootName, fileData.slug!, "/" as SimpleSlug)
     const crumbs: CrumbData[] = [firstEntry]
 
+    if (!folderIndex && options.resolveFrontmatterTitle) {
+      folderIndex = new Map()
+      // construct the index for the first time
+      for (const file of allFiles) {
+        if (file.slug?.endsWith("index")) {
+          const folderParts = file.filePath?.split("/")
+          if (folderParts) {
+            const folderName = folderParts[folderParts?.length - 2]
+            folderIndex.set(folderName, file)
+          }
+        }
+      }
+    }
+
     // Split slug into hierarchy/parts
     const slugParts = fileData.slug?.split("/")
     if (slugParts) {
       // full path until current part
       let currentPath = ""
       for (let i = 0; i < slugParts.length - 1; i++) {
-        let currentTitle = slugParts[i]
+        let curPathSegment = slugParts[i]
 
-        // TODO: performance optimizations/memoizing
         // Try to resolve frontmatter folder title
-        if (options?.resolveFrontmatterTitle) {
-          // try to find file for current path
-          const currentFile = findCurrentFile(allFiles, currentTitle)
-          if (currentFile) {
-            currentTitle = currentFile.frontmatter!.title
-          }
+        const currentFile = folderIndex?.get(curPathSegment)
+        if (currentFile) {
+          curPathSegment = currentFile.frontmatter!.title
         }
+
         // Add current slug to full path
         currentPath += slugParts[i] + "/"
 
         // Format and add current crumb
-        const crumb = formatCrumb(currentTitle, fileData.slug!, currentPath as SimpleSlug)
+        const crumb = formatCrumb(curPathSegment, fileData.slug!, currentPath as SimpleSlug)
         crumbs.push(crumb)
       }