Mongoose: Removing multiple sub documents correct way

[whitecolor]

First I tried the first way:

item.tasks.forEach(function(task){
            if (task.finished)
                tasks.remove(task)
})

item.save() 

but after that I have NOT ALL finished task where deleted.

Then I did with async saving item after each sub doc remove:

        var tasksToRemove= [];
        tasks.forEach(function(task){
            if (task.finished)
                tasksToRemove.push(task)
        })

        async.mapSeries(tasksToRemove, function(task, callback){
            console.log('Removing finished tasks: remove task', task._id )
            tasks.remove(task)
            item.save(function(err){
                callback(err)
            })
        }, function(err){

        })

All tasks where deleted from DB.

What is the issue with first way of removing sub docs?

[whitecolor]

I've managed to to this with pull method (provided there list of task that should be deleted). Is it correct way of deleting? If yes, lets close the ticket.

[aheckmann]

Removing elements from the array during forward iteration causes elements to be skipped over. This is true when using forEach or even a for loop. Instead, iterate the array in reverse manually and it will work the way you expect.

[whitecolor]

"iterate the array in reverse manually" didn't get it, could you explain?

[aheckmann]

sure.

var i = item.tasks.length;
while (i--) {
  var task = item.tasks[i];
  if (blah) {
    item.tasks.remove(task); // or just task.remove()
  }
}

[whitecolor]

Ok, thank you, I got what you mean. Is it possible to use:
task.reverse().forEach( ?

[aheckmann]

no b/c you'll still be iterating forward while removing elements. test it out and see what i mean.

[whitecolor]

Oh, I got it now, thanks =)

[aheckmann]

:)

[manavrajvanshi]

Thank you!