javascript - 从 Javascript 中的回调函数返回

Question

如何从node.js/javascript回调的值中获取返回值？

function get_logs(){
    User_Log.findOne({userId:req.user._id}, function(err, userlogs){
        if(err) throw err;
        if(userlogs){
            // logs = userlogs.logs;
            return "hello there is a logs";
        } else {
            return "there is no logs yet..."
        }
    })
}

var logs = get_logs();
console.log(logs);

Answer 1

您无法从异步执行的函数返回结果。

最简单的解决方案是传递回调:

function get_logs(cb){
    User_Log.findOne({userId:req.user._id}, function(err, userlogs){
        if(err) throw err;
        if(userlogs){
            // logs = userlogs.logs;
            cb("hello there is a logs");
        } else {
            cb("there is no logs yet...)"
        }
    })
}

get_logs(function(logs){
    console.log(logs);
});