Asynchronously find all files matching a filter in a directory using node.

findFiles.js

/**
 *   Walks a filestructure starting from a given root and returns all found files to a callback, using a filter.
 *   @param  {String}   dir    - Root directory
 *   @param  {RegEx}    filter - RegEx to test found files against
 *   @param  {Function} done   - Callback will be called with (err, foundFiles)
 *   @private
 */
function walk(dir, filter, done) {
    var results = [];
    fs.readdir(dir, function(err, list) {
        if (err) return done(err);
        var 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 {
                    if (filter.test(file)) {
                        results.push(file);
                    }
                    if (!--pending) done(null, results);
                }
            });
        });
    });
};