adopted original formatting, added readme entry for how to append custom fields.

Author: lukas

README.md

@@ -164,6 +164,33 @@ photos
 }
 ```
 
+## Adding custom fields
+You can easily extend a `DirectoryTree` object with custom fields by adding them to the custom field.
+For example add an `id` based on the path of a `DirectoryTree` object for each directory and file like so:
+```
+import { createHash } from 'crypto';
+import * as directoryTree from 'directory-tree';
+import { DirectoryTree, DirectoryTreeOptions, DirectoryTreeCallback } from 'directory-tree';
+
+const callback: DirectoryTreeCallback = (
+            item: DirectoryTree,
+            path: string
+        ) => {
+            item.custom.id = createHash('sha1').update(path).digest('base64');
+        };
+
+const dirTree: DirectoryTree & { id?: string } = directoryTree(
+    "<your-directory-path>",
+    {},
+    callback,
+    callback
+);
+
+// to explore the object with the new custom fields
+console.log(JSON.stringify(dirTree, null, 2));
+
+```
+
 ## Note
 
 Device, FIFO and socket files are ignored.

index.d.ts

@@ -1,37 +1,33 @@
 import { Stats } from 'fs';
 
 declare function directoryTree(
-	path: string,
-	options?: directoryTree.DirectoryTreeOptions,
-	onEachFile?: directoryTree.DirectoryTreeCallback,
-	onEachDirectory?: directoryTree.DirectoryTreeCallback
+  path: string,
+  options ? : directoryTree.DirectoryTreeOptions,
+  onEachFile ? : directoryTree.DirectoryTreeCallback,
+  onEachDirectory ? : directoryTree.DirectoryTreeCallback,
 ): directoryTree.DirectoryTree;
 
 export as namespace directoryTree;
 
 declare namespace directoryTree {
-	export interface DirectoryTree {
-		path: string;
-		name: string;
-		size: number;
-		type: 'directory' | 'file';
-		children?: DirectoryTree[];
-		extension?: string;
-		isSymbolicLink?: boolean;
-		custom: { [key: string]: any };
-	}
-	export interface DirectoryTreeOptions {
-		normalizePath?: boolean;
-		exclude?: RegExp | RegExp[];
-		attributes?: (keyof Stats | 'type' | 'extension')[];
-		extensions?: RegExp;
-		followSymlink?: boolean;
-	}
-	export type DirectoryTreeCallback = (
-		item: DirectoryTree,
-		path: string,
-		stats: Stats
-	) => void;
+  export interface DirectoryTree {
+    path: string;
+    name: string;
+    size: number;
+    type: "directory" | "file";
+    children ? : DirectoryTree[];
+    extension?: string;
+    isSymbolicLink?: boolean;
+    custom: { [key: string]: any };
+  }
+  export interface DirectoryTreeOptions {
+    normalizePath ? : boolean;
+    exclude ? : RegExp | RegExp[];
+    attributes ? : (keyof Stats | "type" | "extension")[];
+    extensions ? : RegExp;
+    followSymlink ? : boolean;
+  }
+  export type DirectoryTreeCallback = (item: DirectoryTree, path: string, stats: Stats) => void;
 }
 
 export = directoryTree;