Simulate azure cache and Add expired time function

cache

var CACHE = {};

var cache = function() {
    var self = this;
    self.memory = {};
};

cache.put = function(key, data , cb) {
    var self = this;
    self.memory = {key:data};
    cb(true);
};

cache.get = function(key, cb) {
    var self = this;
    cb(false, self.memory["key"]);
};

//

CACHE.write_json = function(key ,value ,cb) {
    var buf = new Buffer(JSON.stringify(value));
    var json = JSON.stringify(buf);
    var _struct = {
        data: json,
        time: new Date()
    }

    cache.put(key, _struct, function (error) {
        if (error) {
            cb(false);
        } else {
            cb(true);
        }
    });
};

CACHE.check_no_expired = function(write_time, cache_mins) {
    var now = new Date("2014/07/20 20:49");
    var diffs = now - write_time ;
    var diffMins = Math.round(((diffs % 86400000) % 3600000) / 60000);
    console.log("now:"+now);
    console.log("write:"+write_time);
    console.log(diffMins);
    console.log(cache_mins);
    return (diffMins < cache_mins);
};

CACHE.read_json = function(key, cache_time, cb) {
    cache.get(key, function (error, value) {
        console.log(value);
        if (error) {
            cb([], false);
        } else {
            if(!value) { // value is null
                cb([], false);
            } else {
                if(!!value.time) {
                    if(CACHE.check_no_expired(value.time, cache_time)) {
                        var data = new Buffer(JSON.parse(value.data));
                        var json = JSON.parse(data.toString('utf8'));
                        cb(json, true);
                    } else {
                        cb([], false);
                    }
                } else {
                    cb([], false);
                }
            }
        }
    });
};


console.log("write {'data:'a1'} to cache" );
CACHE.write_json("test",{"data":'a1'}, function(error) {
    console.log("has error " + (error)?"yes":"no");
    CACHE.read_json("test", 5,function(data, error) {
        console.log(data);
        console.log(error);
    });
});