[nodejs mongoose 想获得find的值] #异步

nodejs_mongoose.js

function couldSendSMS(mobile) {
 	SMSLog.model.find()
        .where('mobile', mobile)
        .sort({ expiredate: -1 })
        .limit(1)
        .exec( function (err, smsLogs) {
            console.log("find ok");
            return  (smsLogs[0].expiredate < Date.now());
         });
}
    

var isNeedSend = couldSendSMS(mobile);  //为什么isNeedSend 是undefine