Is cache file fresh or not.

cache.js

var fs = require('fs');
var Cache = {

    isFresh: function (file, time, cb) {

        fs.exists(file, function (exists) {
            if (!exists) {
                return cb(null, false);
            }

            fs.stat(file, function(err, stat) {

                var fileTimestamp = stat.mtime.getTime(),
                    currentTime = new Date().getTime();

                if (err) {
                    return cb(err);
                } else {

                    if ((currentTime - fileTimestamp) > time) {
                        return cb(null, false);
                    } else {
                        return cb(null, true);
                    }
                }
            });

        });
    }
};