Nested queries with express/mongoose - node.js

Question

I have a Tag collection, they only have one value which is the label. They can be random tag or a tree tag (here a sample without the _id) :
{
"label": "/test1"
}
{
"label": "/test2"
}
{
"label": "/test1/test1-1"
}
{
"label": "/test2/test2-1"
}
{
"label": "/test1/test1-1/test1-1-1"
}
{
"label": "something"
}
What I want is to have a single object with the tree of my tags :
{
"/test1": {
"name": "test1"
, "children": {
"/test1/test1-1" : {
"name": "test1-1"
, "children": {
"/test1/test1-1/test1-1-1" : {
"name": "test1-1-1"
, "children": {}
}
}
}
}
}
, "/test2": {
"name": "test2"
, "children": {
"/test2/test1-2" : {
"name": "test1-2"
, "children": {}
}
}
}
}
Here is what I tried in my app :
app.get('/tree', function(req, res, next) {
var tree = {};
Tag
// If you have a better solution, I'm not really fan of this
.$where('this.label.split(new RegExp("/")).length === 2')
.exec(function(err, tags) {
tags.forEach(function(tag) {
tag.getChildren(function(children) {
tree[tag.label] = {
'title': tag.label
, 'children': children
}
});
});
});
// do some stuff with the `tree` var
// which does not work because of the asynchronousity of mongo
});
And in my model I have, it doesn't work, at first I wanted to return the path of the tree with with tag.getChildren() but then, I thought a callback will be a better option and I stop there.
Tag.methods.getChildren = function(callback) {
var tree = {};
Tag
.$where('this.label.split(new RegExp("' + this.label + '/")).length === 2')
.exec(function(err, tags) {
tags.forEach(function(tag) {
tag.getChildren(function(children) {
tree[tag.label] = {
'title': tag.label
, 'children': children
}
});
});
return tree
});
};
I have no idea how to to this, I'm fairly new to Node and asynchronous programming so any help will be appreciate.

Answer 1

You probably should look into the async.js module, which has some support for doing an iteration that calls asynchonous code on each step and executing a callback when all the async code is done.

Answer 2

Doing multiple Mongo request is stupid in this example, so I did only one, parse the result and create my tree, here is my code if somebody has the same problem :
app.get('/tree', function(req, res, next) {
var tree = {}
Tag
.find({ label: { $regex: /^\// } }, ['label'])
// Skip the "/"
.skip(1)
.exec(function(err, tags) {
tags.forEach(function(tag) {
var split = tag.label.split('/');
// Root
if (split.length === 2) {
tree[_.slugify(split[1])] = {
title: split[1]
, children: {}
}
} else {
var name = split.pop()
, path = tag.label
, pathSlug = _.slugify(path.replace(/\//g, '-'))
, parentPath = path.split('/')
, parentSlug = ''
, parent;
parentPath.shift();
parentPath.pop();
parentPath.forEach(function(step) {
step = parentSlug ? parentSlug + '-' + _.slugify(step) : _.slugify(step);
parentSlug = step;
parent = parent ? parent.children[step] : tree[step];
});
if (!parent) {
console.error('ERROR :')
console.log(tag.label)
console.log(path.split('/'))
console.log(name)
console.error('##################')
} else {
parent.children[pathSlug] = {
title: name
, children: {}
}
}
}
});
res.send(tree, 200);
});
});