async.each not giving the result? - node.js

Question

This is my code:
var shopId=[1,2,3,4];
async.each(shopId,function (item,callback) {
model.client.query("SELECT categoryId shopId=? ", [shopId], function (err, rows) {
if (rows.length > 0) {
var asyncData = rows;
//categoryId will be in the format [1,2,3,4]
async.each(asyncData,function (item, callback) {
var categoryId = item.categoryId;
async.series([
function (callback) {
model.client.query("select categoryName from category where categoryId = ?", [categoryId], function (err, data) {
callback(null, data);
});
}],
function (err, results) {
item.category = results[0];
callback();
});
},function (err) {
callback(asyncData); //getting data here
});
}
});
},function (err,result) {
res.json(result); //not getting data here
});
I am new to aysnc methods. I am not able to pass the result to final function.

Answer 1

Supposing that there is a shop table, you can join your tables to save a query.
const sql = 'select categoryName from category as c inner join shop as s on c.categoryId = s.categoryId where s.shopId = ?'
then
const shopId = [1, 2, 3, 4];
const finalResult = [];
async.each(shopId, function(item, callback) {
model.client.query(sql, [shopId], function (err, rows) {
// do not forget error handling !
if (rows.length > 0) {
finalResult.push(rows);
return callback();
}
return callback(); // do not forget to return callback in every case
});
}, function(err) { // in async each callback, you only get errors
if (err)
return res.json(err); // or whatever error handling
res.json(finalResult);
});
Also, considering your code, I would advise to name differently your callbacks to avoid errors or forgets. i.e.
async.each([], function(item, cbkGlobal) {
async.each([], function(item, cbkEach) {});
});
And async.series is usefull when you want multiple functions to get execute in order. But here you are executing only one function...