node-async doesn't execute callback

Question

The Code

I tried this package https://www.npmjs.com/package/async to implement series & parallel processing.

For small cases it works, well, however when I try to run this, I get an unexpected behavior:

async.series([
    function(callback){
        console.log('one');
        callback();
    },
    function(callback){
        console.log('two');
        async.parallel([
            function(callback){
                console.log('two-one');
                callback();
            },
            function(callback){
                async.series([
                    function (callback){
                        console.log('two-two-one');
                        callback();
                    },
                    function (callback){
                        console.log('two-two-two');
                        callback();
                    }
                ]);
            }
        ], callback);
    },
    function(callback){
        console.log('three');
        callback();
    }
]);

The Expected Result

The code should print one, two, two-one, and three in series. However, after print two-one, I want to print two-two-one and two-two-two in parallel.

The expected result is either:

one
two
two-one
two-two-one
two-two-two
three

or

one
two
two-one
two-two-two
two-two-one
three

The Real Result

Unfortunately, three is never printed.

one
two
two-one
two-two-one
two-two-two

The Question

Is there something wrong with my code/understanding?

Thanks.

Alexis Tyler · Accepted Answer · 2017-03-09 06:07:53Z

1

Async series take a last argument as function to grab the final result.

Please pass parallel callback as second argument of async series.

async.series([
    function(callback){
        console.log('one');
        callback();
    },
    function(callback){
        console.log('two');
        async.parallel([
            function(callback){
                console.log('two-one');
                callback();
            },
            function(callback){
                async.series([
                    function (callback){
                        console.log('two-two-one');
                        callback();
                    },
                    function (callback){
                        console.log('two-two-two');
                        callback();
                    }
                ],callback);// pass parallel callback to trace the outcome 
            }
        ], callback);
    },
    function(callback){
        console.log('three');
        callback();
    }
],console.log);// use console.lg to get the final outcome of series

edited Mar 9, 2017 at 6:07

Alexis Tyler

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answered Mar 9, 2017 at 4:33

Kundu

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3 Comments

goFrendiAsgard Over a year ago

I just change the line with // pass parallel callback to trace the outcome comment. And it works perfectly. Just now there is a second argument in async.series, and it seems to be undocumented :(. Thx btw

Alexis Tyler Over a year ago

@Kundu please use a 4 space indentation for code blocks instead of backticks.

Kundu Over a year ago

@AlexisTyler Sorry for the inconvenience. I have used a mobile browser to add the answer. Thanks for the edit BTW.

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