import * as fs from "fs"; import recursiveReaddir = require("recursive-readdir"); recursiveReaddir("some/path", (err, files) => {}); recursiveReaddir("some/path", ["foo.cs", "*.html"], (err, files) => {}); function apple(a: string, b: fs.Stats): boolean { return true; } async function banana(): Promise { return recursiveReaddir("some/path", [apple]); }