perf: memoize filetree computation (#490)

* perf: memoize filetree computation

* format

* var -> let

quartz/components/Explorer.tsx

@@ -4,6 +4,7 @@ import explorerStyle from "./styles/explorer.scss"
 // @ts-ignore
 import script from "./scripts/explorer.inline"
 import { ExplorerNode, FileNode, Options } from "./ExplorerNode"
+import { QuartzPluginData } from "../plugins/vfile"
 
 // Options interface defined in `ExplorerNode` to avoid circular dependency
 const defaultOptions = {
@@ -27,49 +28,58 @@ const defaultOptions = {
 } satisfies Options
 
 export default ((userOpts?: Partial<Options>) => {
-  function Explorer({ allFiles, displayClass, fileData }: QuartzComponentProps) {
-    // Parse config
-    const opts: Options = { ...defaultOptions, ...userOpts }
+  // Parse config
+  const opts: Options = { ...defaultOptions, ...userOpts }
 
-    // Construct tree from allFiles
-    const fileTree = new FileNode("")
-    allFiles.forEach((file) => fileTree.add(file, 1))
+  // memoized
+  let fileTree: FileNode
+  let jsonTree: string
 
-    /**
-     * Keys of this object must match corresponding function name of `FileNode`,
-     * while values must be the argument that will be passed to the function.
-     *
-     * e.g. entry for FileNode.sort: `sort: opts.sortFn` (value is sort function from options)
-     */
-    const functions = {
-      map: opts.mapFn,
-      sort: opts.sortFn,
-      filter: opts.filterFn,
-    }
+  function constructFileTree(allFiles: QuartzPluginData[]) {
+    if (!fileTree) {
+      // Construct tree from allFiles
+      fileTree = new FileNode("")
+      allFiles.forEach((file) => fileTree.add(file, 1))
 
-    // Execute all functions (sort, filter, map) that were provided (if none were provided, only default "sort" is applied)
-    if (opts.order) {
-      // Order is important, use loop with index instead of order.map()
-      for (let i = 0; i < opts.order.length; i++) {
-        const functionName = opts.order[i]
-        if (functions[functionName]) {
-          // for every entry in order, call matching function in FileNode and pass matching argument
-          // e.g. i = 0; functionName = "filter"
-          // converted to: (if opts.filterFn) => fileTree.filter(opts.filterFn)
+      /**
+       * Keys of this object must match corresponding function name of `FileNode`,
+       * while values must be the argument that will be passed to the function.
+       *
+       * e.g. entry for FileNode.sort: `sort: opts.sortFn` (value is sort function from options)
+       */
+      const functions = {
+        map: opts.mapFn,
+        sort: opts.sortFn,
+        filter: opts.filterFn,
+      }
 
-          // @ts-ignore
-          // typescript cant statically check these dynamic references, so manually make sure reference is valid and ignore warning
-          fileTree[functionName].call(fileTree, functions[functionName])
+      // Execute all functions (sort, filter, map) that were provided (if none were provided, only default "sort" is applied)
+      if (opts.order) {
+        // Order is important, use loop with index instead of order.map()
+        for (let i = 0; i < opts.order.length; i++) {
+          const functionName = opts.order[i]
+          if (functions[functionName]) {
+            // for every entry in order, call matching function in FileNode and pass matching argument
+            // e.g. i = 0; functionName = "filter"
+            // converted to: (if opts.filterFn) => fileTree.filter(opts.filterFn)
+
+            // @ts-ignore
+            // typescript cant statically check these dynamic references, so manually make sure reference is valid and ignore warning
+            fileTree[functionName].call(fileTree, functions[functionName])
+          }
         }
       }
+
+      // Get all folders of tree. Initialize with collapsed state
+      const folders = fileTree.getFolderPaths(opts.folderDefaultState === "collapsed")
+
+      // Stringify to pass json tree as data attribute ([data-tree])
+      jsonTree = JSON.stringify(folders)
     }
+  }
 
-    // Get all folders of tree. Initialize with collapsed state
-    const folders = fileTree.getFolderPaths(opts.folderDefaultState === "collapsed")
-
-    // Stringify to pass json tree as data attribute ([data-tree])
-    const jsonTree = JSON.stringify(folders)
-
+  function Explorer({ allFiles, displayClass, fileData }: QuartzComponentProps) {
+    constructFileTree(allFiles)
     return (
       <div class={`explorer ${displayClass}`}>
         <button