async.each/forEach third parameter(callback) is triggered after each interval

Question

Hi
I have function that accepts an two arrays and callback function, I am iterating over one of the arrays using async.each(and tried async.forEach and both have same result), everything works fine but the callback that I am receiving as the parameter, which is sent as the third parameter is triggered after the first iteration. Here is my code.

 function itemLikes(instruments,likes, finalCallback){ var items = []; if(instruments.length >= 1){ async.forEach(instruments, function(instrument,cb){ if(likes){ if(likes.indexOf(instrument._id.toString()) !== -1){ instrument.liked = 1; cb(items.push(instrument)) } else{ cb(items.push(instrument)) } } else{ cb(items.push(instrument)) } }, function(err){ finalCallback(items) }) } else{ finalCallback(items) } 

}

This is what I understood from the documentation, but my finalCallback is triggered right after my first iteration completes.

Thanks and Regards.

Answer 1

The reason the callback that receiving as the parameter (finalCallback()) is triggered after the first iteration is because asyc.each()'s callback (cb) is called with a non-null value. When it's called with a non-null value, async.each()'s final callback gets called which then calls your finalCallback(). You need to do something like this:

if(likes){
  if(likes.indexOf(instrument._id.toString()) !== -1){
    instrument.liked = 1;
    items.push(instrument);
    cb()
  } else{
    items.push(instrument);
    cb()
  }
} else{
  items.push(instrument);
  cb()
}

It seems like your logic above can be simplified as following:

if(likes && likes.indexOf(instrument._id.toString()) !== -1){
    instrument.liked = 1;
}
items.push(instrument);
cb()