Question

我有下一个代码：

exports.getCommunities = function(user, callback)
{      //I am getting the communities for a user.
        community_users.find({'user':user}).sort({_id : 1 }).toArray(function(err, docs) {
            docs.sort
            var clas = [];
            //for each community, I need to find the country of that community and add it to each docs object. To do so, i call a getCommunityByName function that finds the community document in the communities mongodb collection by a given name.
            docs.forEach(function(entry,i) {
                clas.push(entry);
                getCommunityByName(entry.name, function(e, o){
                    if (o){
                        clas[i].country = o.country;
                        if (docs.length-1 == i) {callback(null,clas)}
                    } else { console.log('community-not-found: '+entry.name)}
                });

            });

        }); 
};

我的行为很奇怪。想象一下，docs是一个7对象数组。我正在获得一个7位阵列，但是随机数有阵列。有时只有3个有国家/地区密钥，有时是5个，有时是6个......

我认为调用回调的if语句不是等待每次调用getCommunityByName而我不知道为什么......

我需要一些亮点...

此致

Answer 1

假设getCommunityByName执行异步请求，可能是对最终项目的请求在某些先前项目之前返回，因此它很快就会调用回调。而不是使用循环中的i来决定何时回拨，而是倒计时返回的请求并在它们全部完成时调用回调：

exports.getCommunities = function(user, callback)
{      //I am getting the communities for a user.
    community_users.find({'user':user}).sort({_id : 1 }).toArray(function(err, docs) {
        docs.sort
        var clas = [];
        //for each community, I need to find the country of that community and add it to each docs object. To do so, i call a getCommunityByName function that finds the community document in the communities mongodb collection by a given name.

        //initialise counter to number of items
        var counter = docs.length;
        docs.forEach(function(entry,i) {
            clas.push(entry);
            getCommunityByName(entry.name, function(e, o) {

                //request returned, decrement counter
                counter--;
                if (o){
                    clas[i].country = o.country;
                } else { console.log('community-not-found: '+entry.name)}
                if (counter == 0) {
                    //All requests returned, fire callback
                    callback(null, clas);
                }
            });

        });

    }); 
};

Javascript奇怪的行为，异步问题？

1 个答案: