List all files in a directory in Node.js recursively in a synchronous fashion

walksync.js

// List all files in a directory in Node.js recursively in a synchronous fashion
var walkSync = function(dir, filelist) {
  var fs = fs || require('fs'),
      files = fs.readdirSync(dir);
  filelist = filelist || [];
  files.forEach(function(file) {
    if (fs.statSync(dir + file).isDirectory()) {
      filelist = walkSync(dir + file + '/', filelist);
    }
    else {
      filelist.push(file);
    }
  });
  return filelist;
};

TypeScript version with filters:

import {readdirSync, statSync} from "node:fs";
import * as path from "node:path";

/**
 * Options for scanning a directory.
 *
 * @template PathType - The type of the relative directory path.
 * @interface DirectoryScanOptions
 * @property {string | PathType} [baseDir=""] - The base directory for relative paths.
 * @property {string[]} [fileExtensions=[]] - An array of file extensions to filter.
 * @property {"all" | "dir" | "file"} [collectionType="all"] - Specifies what to collect:
 *   - "all": collect both files and directories
 *   - "dir": collect only directories
 *   - "file": collect only files
 */
interface DirectoryScanOptions<PathType extends string = ""> {
    /**
     * Optional relative directory path
     *
     * The base directory for relative paths.
     *
     * @default ""
     */
    baseDir?: string | PathType;

    /**
     * Optional array of file extensions
     *
     * An array of file extensions to filter.
     * 
     * @default []
     */
    fileExtensions?: string[];

    /**
     * Optional collection type
     *
     * Specifies what to collect:
     *  - "all": collect both files and directories
     *  - "dir": collect only directories
     *  - "file": collect only files
     *
     *  @default "all"
     */
    collectionType?: "all" | "dir" | "file";
}

interface ScanDirectory {

    /**
     * Scans a directory and collects paths based on specified options.
     *
     * @template PathType - The type of the directory path.
     * @param {PathType} targetDir - The path of the directory to scan.
     * @returns {string[]} - An array of collected paths relative to the specified directory.
     *
     * @example
     * // Example usage of scanDirectory function
     * const collectedPaths = scanDirectory('/path/to/directory', {
     *     baseDir: '/path/to',
     *     fileExtensions: ['.js', '.ts'],
     *     collectionType: 'file'
     * });
     * console.log(collectedPaths); // Outputs an array of relative file paths
     */
    <PathType extends string>(targetDir: PathType): string[];

    /**
     * Scans a directory and collects paths based on specified options.
     *
     * @template PathType - The type of the directory path.
     * @param {PathType} targetDir - The path of the directory to scan.
     * @param {DirectoryScanOptions<PathType>} [options] - Options for scanning the directory.
     * @returns {string[]} - An array of collected paths relative to the specified directory.
     *
     * @example
     * // Example usage of scanDirectory function
     * const collectedPaths = scanDirectory('/path/to/directory', {
     *     baseDir: '/path/to',
     *     fileExtensions: ['.js', '.ts'],
     *     collectionType: 'file'
     * });
     * console.log(collectedPaths); // Outputs an array of relative file paths
     */
    <PathType extends string>(targetDir: PathType, options: DirectoryScanOptions<PathType>): string[];
}

/**
 * Scans a directory and collects paths based on specified options.
 *
 * @template PathType - The type of the directory path.
 * @param {PathType} targetDir - The path of the directory to scan.
 * @param {DirectoryScanOptions<PathType>} [options] - Options for scanning the directory.
 * @returns {string[]} - An array of collected paths relative to the specified directory.
 *
 * @example
 * // Example usage of scanDirectory function
 * const collectedPaths = scanDirectory('/path/to/directory', {
 *     baseDir: '/path/to',
 *     fileExtensions: ['.js', '.ts'],
 *     collectionType: 'file'
 * });
 * console.log(collectedPaths); // Outputs an array of relative file paths
 */
export const scanDirectory: ScanDirectory = <PathType extends string>(
    targetDir: PathType, // The directory path to scan
    options?: DirectoryScanOptions<PathType> // Options for scanning a directory.
): string[] => {

    const {
        baseDir = "", // The base directory for relative paths
        fileExtensions = [], // Default to an empty array if no extensions are provided
        collectionType = "all" // Default to collecting all types
    } = options || {};

    // Type alias for the collection options
    type CollectionArray = Array<typeof collectionType>;

    // Array to hold the scanned paths
    const collectedPaths: string[] = [];
    // Read directory contents
    const directoryContents = readdirSync(targetDir, {withFileTypes: true, recursive: true});
    // Check if any extensions are provided
    const hasExtensions = !!fileExtensions?.length;

    // Iterate over each file/directory in the scanned directory
    for (const directoryEntry of directoryContents) {
        // Construct the full file path
        const fullPath = path.join(directoryEntry.parentPath, directoryEntry.name);
        // Get the file statistics
        const fileStats = statSync(fullPath);
        // Get the relative path
        const relativePath = path.relative(baseDir, fullPath);

        // Check if we should collect files
        if ((["all", "file"] as CollectionArray).includes(collectionType) && fileStats.isFile()) {
            // If extensions are specified, check if the file matches
            if (hasExtensions && !fileExtensions.includes(path.extname(fullPath))) {
                continue; // Skip this file if it doesn't match the extensions
            }
            // Add the relative file path to the collected array
            collectedPaths.push(relativePath);
        }
        // Check if we should collect directories
        else if ((["all", "dir"] as CollectionArray).includes(collectionType) && fileStats.isDirectory()) {
            // Add the relative directory path to the collected array
            collectedPaths.push(relativePath);
        }
    }

    // Return the collected paths
    return collectedPaths;
};

Vanilla JS version if you don't use TypeScript:

import {readdirSync, statSync} from "node:fs";
import * as path from "node:path";

/**
 * Scans a directory and collects paths based on specified options.
 *
 * @template PathType - The type of the directory path.
 * @param {PathType} targetDir - The path of the directory to scan.
 * @param {DirectoryScanOptions<PathType>} [options] - Options for scanning the directory.
 * @returns {string[]} - An array of collected paths relative to the specified directory.
 *
 * @example
 * // Example usage of scanDirectory function
 * const collectedPaths = scanDirectory('/path/to/directory', {
 *     baseDir: '/path/to',
 *     fileExtensions: ['.js', '.ts'],
 *     collectionType: 'file'
 * });
 * console.log(collectedPaths); // Outputs an array of relative file paths
 */
export const scanDirectory = (
    targetDir, // The directory path to scan
    options // Options for scanning a directory.
) => {
    const {
        baseDir = "", // The base directory for relative paths
        fileExtensions = [], // Default to an empty array if no extensions are provided
        collectionType = "all" // Default to collecting all types
    } = options || {};

    // Array to hold the scanned paths
    /** @type {string[]} */
    const collectedPaths = [];
    // Read directory contents
    /** @type {Dirent[]} */
    const directoryContents = readdirSync(targetDir, {withFileTypes: true, recursive: true});
    // Check if any extensions are provided
    /** @type {boolean} */
    const hasExtensions = !!fileExtensions?.length;

    // Iterate over each file/directory in the scanned directory
    for (const directoryEntry of directoryContents) {
        // Construct the full file path
        /** @type {string} */
        const fullPath = path.join(directoryEntry.parentPath, directoryEntry.name);
        // Get the file statistics
        /** @type {Stats} */
        const fileStats = statSync(fullPath);
        // Get the relative path
        /** @type {string} */
        const relativePath = path.relative(baseDir, fullPath);
        // Check if we should collect files
        if (["all", "file"].includes(collectionType) && fileStats.isFile()) {
            // If extensions are specified, check if the file matches
            if (hasExtensions && !fileExtensions.includes(path.extname(fullPath))) {
                continue; // Skip this file if it doesn't match the extensions
            }
            // Add the relative file path to the collected array
            collectedPaths.push(relativePath);
        }
        // Check if we should collect directories
        else if (["all", "dir"].includes(collectionType) && fileStats.isDirectory()) {
            // Add the relative directory path to the collected array
            collectedPaths.push(relativePath);
        }
    }
    // Return the collected paths
    return collectedPaths;
};

// JSODC types

/**
 * Options for scanning a directory.
 *
 * @template PathType - The type of the relative directory path.
 * @interface DirectoryScanOptions
 * @property {string | PathType} [baseDir=""] - The base directory for relative paths.
 * @property {string[]} [fileExtensions=[]] - An array of file extensions to filter.
 * @property {"all" | "dir" | "file"} [collectionType="all"] - Specifies what to collect:
 *   - "all": collect both files and directories
 *   - "dir": collect only directories
 *   - "file": collect only files
 */

$ yarn add glob rxjs

/* --- */

import {Observable, of} from 'rxjs';
import { mergeMap } from 'rxjs/operators';
import * as path from 'path';
import {glob, type GlobOptionsWithFileTypesUnset} from "glob";

const listFiles = (root: string, globMask = '*', ignoredFolders: string[] = []): Observable<string> => {
  const ignore = ignoredFolders.map(x => path.join(root, x));
  const options: GlobOptionsWithFileTypesUnset = {
    cwd: root,
    nodir: true,
    ignore: ignore,
  };

  // do not use path.join as it uses upper slash instead of lower slash, and it does not work
  return of(globMask).pipe(
    mergeMap(x=> glob(x, options)),
    mergeMap(x => x),
  );
}

/* --- */

const topLevel = listFiles('/dev/sdb', '*.ts', []).subscribe(x => { console.log(x); });
const recurse = listFiles('/dev/sdb', '**/*.ts', []).subscribe(x => { console.log(x); });

I just want to say that every time someone comes up with another solution to this problem it makes my day :)

wow.. been receiving notifications for this thing for 9 years!.. it's the most consistent item in my dev career

There are only 3 hard problems in computer science... cache invalidation, naming things, off by one errors, and directory walking,