Any better solution about asynchronous query form main table and sub table? - node.js

Question

I have two tables, tb_article and tb_attach_url, like this
==============tb_article=================
id title content
1 "echo" "test"
2 "foo" "bar"
==============tb_attach_url==============
id article_id url_val
1 2 "http://.../foo.png"
2 2 "http://.../bar.png"
3 1 "http://.../test.png"
My scenario is like this,
I want show a list of tb_article,
but tb_attach_url's information need also.
My solution is like this:
function load_article_urls(id, idx, callback){
connection.query("select url_str from tb_attach_url where article_id = ?", [id], function(err, results){
if (err) throw err;
var images = [];
for (var j = 0; j < results.length; j++){
images.push(results[j]["url_str"]);
}
callback(idx, images)
});
}
function load_article(req, res){
connection.query('select * from tb_article where id = ?', [req.query.id], function(err, results){
if (err) throw err;
var cnt = 0;
for (var i = 0; i < results.length; i++){
load_article_urls(results[i].id, i, function(idx, urls){
results[idx]["urlset"] = urls;
cnt++;
if (cnt == results.length){
//waiting for all back
res.render('list_article', { article_list: results});
}
});
}
});
}
I think this implement is little ugly, and want to know some better ways.
Thanks for any help.

Answer 1

You can use async.map (GitHub) to do something like this:
async.map(results,
function (err, callback) { /* Call callback with the urls as a parameter here */ },
function (err, allUrls) {
// Combine results and allUrls - they are in the same order.
})
Or use some of the other functionalities of async to achieve a similar effect.