All all the files in a folder and sub folders

listFilesRecursive.test.ts

import path from "path";

import { listFiles } from "./listFiles";

/**
 └── test
    ├── file1.txt
    └── folder1
        └── file2.txt
 */

describe("list files", () => {
    test("list files in /helpers", async () => {
        const files = await listFiles({
            dir: path.join(module.path.replace("/.build", ""), "./test"),
        });
        expect(files.join(",")).toContain("file1");
        expect(files.join(",")).toContain("file2");
    });
});

listFilesRecursive.ts

import fs from "fs/promises";
import { flattenDeep, zip } from "lodash";
import path from "path";

interface ListFilesParams {
    dir: string;
}

export const listFiles = async ({
    dir,
}: ListFilesParams): Promise<string[]> => {
    let files: string[] = [];
    for (const fileOrDir of await fs.readdir(dir)) {
        const fullPath = path.join(dir, fileOrDir);
        if ((await fs.lstat(fullPath)).isDirectory()) {
            files = [...files, ...(await listFiles({ dir: fullPath }))];
        } else {
            files = [...files, fullPath];
        }
    }
    const list = await fs.readdir(dir);
    const stats = await Promise.all(
        list.map((l) => fs.lstat(path.join(dir, l))),
    );
    const allFiles = await Promise.all(
        zip(list, stats).map(([fileOrDir, lstat]) => {
            const fullPath = path.join(dir, fileOrDir!);
            if (lstat!.isFile()) {
                return Promise.resolve(fullPath);
            }
            if (lstat!.isDirectory()) {
                return listFiles({ dir: fullPath });
            }
            return "";
        }),
    );
    return flattenDeep(allFiles.filter((a) => a));
};