Set json array in nodejs async - arrays

Question

I am new in nodejs and I want to make a json array by comparing id inside a loop but the MongoDB function does not wait for the loop to complete, so data is not coming out properly. It displays the data before the loop ends, below is the code:
router.get('/getallcountrydataup',function(req, res) {
Country
.where('isDeleted').equals(false)
.exec(function(err,cData){
if (!cData) {
res.json({'status':0,'message': 'No data found','data':[]});
} else{
async.waterfall([
function (done) {
var countryalldata = [];
for (var i = 0; i < cData.length; i++) {
var country_s = cData[i];
State.where('s_c_id').equals(country_s._id)
.exec(function(err, statedata){
country_s.statecount = statedata.length;
//console.log(country_s._id);
console.log(country_s.statecount);
});
countryalldata.push(country_s);
}
done(err, countryalldata);
// console.log(countryalldata);
},
function (countryalldata, done) {
console.log(countryalldata);
res.json({
'status': 1,
'message': 'Data found',
'data': countryalldata
});
}
]);
}
});
});
Here is output of the countryalldata variable printed before the loop will complete. I want to print its output after loop execution is complete.

Answer 1

State.where is asynchronous so it should be synchronized. For example with async.map
router.get('/getallcountrydataup',function(req, res) {
Country
.where('isDeleted').equals(false)
.exec(function(err,cData){
if (!cData) {
res.json({'status':0,'message': 'No data found','data':[]});
} else {
async.waterfall([
function (done) {
async.map(cData, function (country_s, done2) {
// Convert country_s into plain object. It's not a mongoose
// model anymore
country_s = country_s.toObject();
State.where('s_c_id')
.equals(country_s._id)
.exec(function(err,statedata){
if (err) {
done2(err);
return;
}
country_s.statecount = statedata.length;
console.log(country_s.statecount);
done2(null, country_s)
});
}, function(err, countryalldata) {
if (err) {
done(err);
}
else {
done(null, countryalldata)
}
});
},
function (countryalldata, done) {
console.log(countryalldata);
res.json({'status':1,'message': 'Data found','data':countryalldata});
}
]);
}
});
});