read files recursively Node Recursive File List

recursiveFileList.js

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

const walk = function(dir, done) {
    let results = [];
    fs.readdir(dir, function(err, list) {
        if (err) return done(err);
        let pending = list.length;
        if (!pending) return done(null, results);
        list.forEach(function(file) {
            file = path.resolve(dir, file);
            fs.stat(file, function(err, stat) {
                if (stat && stat.isDirectory()) {
                    walk(file, function(err, res) {
                        results = results.concat(res);
                        if (!--pending) done(null, results);
                    });
                } else {
                    results.push(file);
                    if (!--pending) done(null, results);
                }
            });
        });
    });
};
const walkSync = async dir => {
    return new Promise(resolve => {
        walk(dir, (b, z) => resolve(z));
    });
};
(async () => {
    const z = await walkSync("./devops");
    let zl = z.filter(e => e.includes(".php"));
    for (let f in zl) {
        let file = zl[f];
        let fname = file.split("/").pop();
        await fs.copyFileSync(file, "./backup/" + fname);
    }
})();