node get files from directory asynchronously and recursively with promises

fs-readdir-recursive.js

/*
 * License: MIT
 * Author: Tony Brix, https://Tony.Brix.ninja
 * Description: Get files from directory asynchronously and recursively with promises.
 */

var fs = require("fs");
var path = require("path");

module.exports = {
	getFiles: function (filePath) {
		return new Promise((resolve) => {
			fs.stat(filePath, (err, stats) => {
				if (err) {
					throw err;
				}
				if (stats.isFile()) {
					resolve([filePath]);
				} else {
					fs.readdir(filePath, (err, files) => {
						if (err) {
							throw err;
						}
						Promise.all(files.map((file) => {
								return this.getFiles(path.resolve(filePath, file));
							}))
							.then((files) => {
								// files will  be an array of arrays.
								// We want to change it to a flat array.
								resolve([].concat.apply([], files));
							});
					});
				}
			});
		});
	}
};