Asynchronous folder traversal

fsutil.js

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

var desc = function(onfinish, counter) {
    if (--counter[0] < 0) {
        if ("function" === typeof onfinish) {
            onfinish();
        }
    }
}

var dirTraversalRecursive = function(dir, callback, onfinish, counter) {
    fs.readdir(dir, (err, files) => {
        if (!err && "undefined" !== typeof files && files instanceof Array) {
            files.forEach(filename => {
                var fullpath = path.join(dir, filename);
                counter[0]++;
                fs.stat(fullpath, (err, stat) => {
                    if (err)
                        desc(onfinish, counter);
                    if (stat.isDirectory()) {
                        dirTraversalRecursive(fullpath, callback, onfinish, counter);
                    } else {
                        setTimeout(() => {
                            callback(filename, dir, fullpath);
                            desc(onfinish, counter);
                        }, 0);
                    }
                });
                
            });
        }
        desc(onfinish, counter);
    });
    
};

/**
 * Traverse in target directory
 * @param {string}   dir
 * @param {(filename:string, dir:string, fullpath:string)=> number} callback
 * @param {function} onfinish
 */
var dirTraversal = function(dir, callback, onfinish) {
    // A counter as a number shall not be passed reference.
    var counter = [0];
    dirTraversalRecursive(dir, callback, onfinish, counter);
};

exports.dirTraversal = dirTraversal;