How to return a result of async function (async module) in nodeJs

Question

I used async module for my project. This is my code in file 1

exports.check = function(option){
    var object = {};
    async.parallel([
        function(callback){
            if(!option.one){callback(null, true);}else{ callback(null, false);}
        },
        function(callback){
            if(!option.two){callback(null, true);}else{ callback(null, false);}
        },
        function(callback){
            if(!option.three){callback(null, true);}else{ callback(null, false);}
        }
    ],
    function(err, results){
        if(results[0] && results[1] && results[2] ){
            object.one = results[0];
            object.two = results[1];
            object.three = results[2];
            object.total = true;

        }else{
            object.one = results[0];
            object.two = results[1];
            object.three = results[2];
            object.total = false;

        }
    })
    return object;
}

And This is code in file 2. I use function in file 1:

var isexit = db.check(option);
    console.log(isexit);

A problem is console is 'undefined'. If I change code in file 1 to be the line (return object):

exports.check = function(option){
    var object = {};
    async.parallel([
        function(callback){
            if(!option.one){callback(null, true);}else{ callback(null, false);}
        },
        function(callback){
            if(!option.two){callback(null, true);}else{ callback(null, false);}
        },
        function(callback){
            if(!option.three){callback(null, true);}else{ callback(null, false);}
        }
    ],
    function(err, results){
        if(results[0] && results[1] && results[2] ){
            object.one = results[0];
            object.two = results[1];
            object.three = results[2];
            object.total = true;

        }else{
            object.one = results[0];
            object.two = results[1];
            object.three = results[2];
            object.total = false;

        }
       return object;
    })

}

It will error. So How to return a funciton result in file 1. Pls help. Thanks so much!

acroca · Accepted Answer · 2015-04-01 09:29:05Z

2

You can't just return it, you'll have to provide a callback for your function:

exports.check = function(option, callback){
  async.parallel([
    //...
  ], function(err, results){
    var object = {};
    //...
    callback(err, object);
  });
}

Then your call will look like:

db.check(option, function(isexit){
  console.log(isexit);
});

answered Apr 1, 2015 at 9:29

acroca

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1 Comment

Hudo Over a year ago

Thank you for helping! Because I want to check to call another function. I have many functions. So I must call check function when I want to check different function. So Could you advise for me to solve this problem?. use return .when i don' use async. Thanks!

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