Waiting for asynchronous task to complete nodejs - node.js

Question

I am creating an application where a user can have many rooms and each room can have many channels, here is my code when retrieving the rooms and corresponding channels:
getRooms: function (req, res) {
User.find({id: req.cookies.claver_id}).exec(function (err, result) {
if (err) {
return res.send(400);
}
rooms = result[0].rooms;
if (rooms.length === 1) {//No room defaults to ['']
return res.send(400);
}
var roomsObj = {};
var roomsArr = [];//we will place the roomsObj inside the roomsArr
var chansObj = {};
var chansArr = [];
async.each(rooms, function (roomId, cb){
roomsObj = {};
if (roomId !== '') {
Rooms.findOne({id: roomId}).exec(function (err, room){
roomName = room.name;
inviteLink = room.inviteLink;
roomsObj.name = roomName;
roomsObj.id = roomId;
roomsObj.inviteLink = inviteLink;
var channels = room.channels;
async.each(channels, function (channelId, cb) {
chansObj = {};
Channels.findOne({id: channelId}).exec(function (err, channel){
chansObj.name = channel.channelName;
chansObj.id = channelId;
chansObj.type = channel.channelType;
chansArr.push(chansObj);
cb();
});
},
function (err) {
});
});
}
cb();
}, function (err) {
roomsObj.channels = chansArr;
roomsArr.push(roomsObj);
sails.log(roomsArr);
});
});
}
It is suppose to return a javascript object with the following structure:
[ { name: "Room Name",
roomId: "Room Id",
inviteLink: "Room Invite Link",
channels: [
{
name: "Channel Name",
id: "channel Id"
}
]
}
]
But I always get an empty array because async.each(rooms, function (roomId, cb){ }) does not wait for async.each(channels, function (channelId, cb) {}) to complete, so I have empty room object. Please how do I solve this issue ?

Answer 1

You should call your rooms's callback loop after completing you channels loop.
You should do something like this:
getRooms: function (req, res) {
User.find({id: req.cookies.claver_id}).exec(function (err, result) {
if (err) {
return res.send(400);
}
rooms = result[0].rooms;
if (rooms.length === 1) {//No room defaults to ['']
return res.send(400);
}
var roomsObj = {};
var roomsArr = [];//we will place the roomsObj inside the roomsArr
var chansObj = {};
var chansArr = [];
async.each(rooms, function (roomId, callback1){
roomsObj = {};
if (roomId !== '') {
Rooms.findOne({id: roomId}).exec(function (err, room){
roomName = room.name;
inviteLink = room.inviteLink;
roomsObj.name = roomName;
roomsObj.id = roomId;
roomsObj.inviteLink = inviteLink;
var channels = room.channels;
var i=0;
async.each(channels, function (channelId, callback2) {
chansObj = {};
Channels.findOne({id: channelId}).exec(function (err, channel){
chansObj.name = channel.channelName;
chansObj.id = channelId;
chansObj.type = channel.channelType;
chansArr.push(chansObj);
i++;
if(i===(channels.length-1)){
i=0;
callback1();
}else{
callback2();
}
});
},
function (err) {
});
});
}
}, function (err) {
roomsObj.channels = chansArr;
roomsArr.push(roomsObj);
sails.log(roomsArr);
});
});
}

Answer 2

I solved it, it really was a case for promises, I used bluebird promise combined with async - the modified code:
getRooms: function (req, res) {
User.find({id: req.cookies.claver_id}).exec(function (err, result) {
if (err) {
return res.send(400);
}
rooms = result[0].rooms;
if (rooms.length === 1) {//No room defaults to ['']
return res.send(400);
}
var roomsObj = {};
var roomsArr = [];//we will place the roomsObj inside the roomsArr
var chansObj = {};
var chansArr = [];
Promise.each(rooms, function (roomId, callback1){
roomsObj = {};
if (roomId !== '') {
async.series ([
function () {
Rooms.findOne({id: roomId}).then(function (room){
roomName = room.name;
inviteLink = room.inviteLink;
roomsObj.name = roomName;
roomsObj.id = roomId;
roomsObj.inviteLink = inviteLink;
channels = room.channels;
sails.log(roomName);
})
}
]);
return Promise.each(channels, function (channelId) {
return Promise.all([
Channels.findOne({id: channelId}).then(function (channel){
chansObj = {};
chansObj.name = channel.channelName;
chansObj.id = channelId;
chansObj.type = channel.channelType;
chansArr.push(chansObj);
sails.log(chansObj);
})
]).then(function () {
sails.log('done one');
});
}).then(function () {
roomsObj.channels = chansArr;
roomsArr.push(roomsObj);
sails.log('done all');
chansArr = [];
});
}
}).then(function () {
sails.log(roomsArr);
sails.log("grand finish");
});
});
}
Thanks to everyone who contributed.