How to implement Async with Mongoose method - node.js

Question

I've got following code now:
exports.listByUser = function(req, res) {
Attack.find({user: req.user._id}, function(err, attacks) {
if(err)
return next(err);
for(var i in attacks) {
attacks[i].evaluateFight();
}
res.json(attacks);
});
};
the main problem is that attacks[i].evaluateFight() is called asynchronously, I want to transform it to make sure that [i-1] iteration is done ... and finally call res.json(attacks). I think, it can be done with async, but I don't know how :( Something like this should work, but how can I call attacks.method?
async.eachSeries(attacks, function (callback) {
//something??
callback();
}, function (err) {
if (err) { throw err; }
res.json(attacks);
});

Answer 1

You can leverage async whilst method call to implement the same. However, there is question I have about the callback of evaluateFight because if it is executed asynchronously then there has to be some callback associated with it which will notify if the previous call is succeeded.
The example code can be as follows assuming evaluateFight returns a callback when completed -
exports.listByUser = function(req, res) {
Attack.find({user: req.user._id}, function(err, attacks) {
if(err)
return next(err);
var attacksLength = attacks.length;
var count = 0;
async.whilst(function () {
return count < attacksLength;
},
function (callback) {
attacks[count].evaluateFight(function(err, result){
count++;
callback();
}); // assuming it returns a callback on success
},
function (err) {
// all the iterations have been successfully called
// return the response
res.json(attacks);
});
};