nodejs async two arrays and mongoose find

Question

I am trying to use async module on my nodejs application with not lucky.

Suppose i have the following:

/**
* parents=['parent1Template','parent2TEmplate',...]
* children=[[{id: 'child1Parent1'}{id: 'child2Parent1'}],[{id: 'child1Parent2"}{id: 'child2Parent2'}],...]
* 
*/
function createTemplate(parents,children){
     var final=[]
     async.each(Object.keys(parents), function(item,done){
                 if(children[item].length!==0) addChildsByParent(parents[item],children[item], function (result) {
                     final.push(result);
                 });
                 done();
     });
         console.log("Final results: "+final);
 return final;
}


function addChildsByParent (parent,childs,callback){
     var template=[];
      //some operations..        

    async.each(childs,function(child){
        Children.findone({"_id": child.id}, function (err,ch)){
              template.push(ch);
        }
    });
    return callback(template)
}

I need to get in final all results when all operations have finished. I have seen also functions as parallel and waterfall on async module but the main problem is that i need to work always with two arrays and do the query when i get the single value.

What's the best way, maybe something like this?

 async.waterfall([ 
   each()...
   async.waterfall([  
      each()...   
   ]) 
 ])

manuelmhtr · Accepted Answer · 2015-01-25 21:36:11Z

I would use async map instead of each to build the response array using the map callback. Also, I would use async parallel instead of waterfall to improve speed, since operations don't depend on each other and can be executed in parallel.

async.parallel({
    final : function(next) {
        async.map(Object.keys(parents), function(item,done){
            if(children[item].length!==0) addChildsByParent(parents[item],children[item], function (result) {
                done(null, result);
            });
        }, next);
    },
    template : function(next) {
        async.map(childs, function(child, done) {
            Children.findone({"_id" : child.id}, function (err, ch) {
                done(err, ch);
            });
        });
    }
}, function(error, results){
    if (!error) {
        console.log(results);
        // This will be {final:[], template:[]}
    }
});

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