Convert flat data into hierarchy in mongodb using Mongoose - node.js

Question

I have created a model which has following properties:
id
children
parent
If the parent is set to null the document will be treated as top level parent. Each document may or may not have list of children which just contains the id's of other document.
db.categories.insert( { _id: "MongoDB", children: [],name: '', parent: 'Databases'} )
db.categories.insert( { _id: "dbm", children: [], parent: 'Databases' } )
db.categories.insert( { _id: "Databases", children: [ "MongoDB", "dbm" ], parent: 'Programming' } )
db.categories.insert( { _id: "Languages", children: [], parent: 'Programming' } )
db.categories.insert( { _id: "Programming", children: [ "Databases", "Languages" ],parent: 'books' } )
db.categories.insert( { _id: "Books", children: [ "Programming" ],parent: null } )
from the above model, I need to generate an output like this:
{
name: "books",
nodes: [
{
name: "Programming",
nodes: [
{
name: "Databases",
nodes: [
{
name: "MonogoDB"
},
{
name: "dbm"
}
]
},
{
name: "Languages"
}
]
}
]
}
So far I have tried this, but because of async nature of findByID(), I am not getting the desired result.Please suggest changes.
myDoc.find({
parent: null
}, function (err, topics) {
if (err) {
return handleError(res, err);
}
var docTree = [];
_.each(document, function(parentDoc) {
var doc = {};
doc.text = parentDoc.name;
doc.nodes = [];
_.each(parentDoc.children, function(child) {
doc.nodes.push(processChildren(child));
});
docTree.push(doc);
});
function processChildren(child) {
myDoc.findById(child, function (err,item) {
var doc = {};
doc.name = item._doc.name;
doc.nodes = [];
if (item._doc.children === null) {
return topic;
} else {
_.each(item._doc.children, function (chld) {
processChildren(chld);
});
}
return doc;
});
};

Answer 1

You can try calling the lean() method after the find() method since documents returned from queries with the lean option enabled are plain JavaScript objects. You can then manipulate those objects to get the hierarchical structure you want. The following may not give the exact desired result but will push you into the right direction:
Model.find({}).lean().exec(function (err, docs) {
if (err) {
return handleError(res, err);
}
var i, len, temp, top_level, id, parent, hierarchical, nodePendingObj, doc, _id, _parent, _children;
i = 0;
top_level = [];
temp = {};
obj = {};
nodePendingObj = {};
_id = '_id';
_parent = 'parent';
_children = 'children';
_.each(docs, function(doc) {
id = doc['_id'];
parent = doc[_parent];
temp[id] = doc;
if (parent === undefined || parent === null) {
obj["name"] = id;
obj["nodes"] = doc[_children];
top_level.push(obj);
}
else {
if (temp[parent] !== undefined) {
if (temp[parent][_children] === undefined) {
temp[parent][_children] = [];
}
var o = {};
o["name"] = id;
if (doc[_children].length !== 0) o["nodes"] = doc[_children];
temp[parent][_children].push(o);
} else {
if (nodePendingObj[parent] === undefined) {
nodePendingObj[parent] = [];
}
var o = {};
o["name"] = id;
if (doc[_children].length !== 0) o["nodes"] = doc[_children];
nodePendingObj[parent].push(o);
}
delete doc[_parent];
}
if (nodePendingObj[id] !== undefined) {
var len = nodePendingObj[id].length;
if (doc[_children] === undefined) {
doc[_children] = [];
}
while (len-- > 0) {
doc[_children].push(nodePendingObj[id].shift());
}
}
});
if (top_level.length === 1) {
hierarchical = top_level[0];
} else if (top_level.length > 1) {
hierarchical = {};
hierarchical[_children] = top_level;
} else {
hierarchical = {};
}
console.log(JSON.stringify(hierarchical));
});
Check the demo below.
var documents = [
{
"_id" : "MongoDB",
"children" : [],
"name" : "",
"parent" : "Databases"
},{
"_id" : "dbm",
"children" : [],
"parent" : "Databases"
},{
"_id" : "Databases",
"children" : [
"MongoDB",
"dbm"
],
"parent" : "Programming"
},{
"_id" : "Languages",
"children" : [],
"parent" : "Programming"
},{
"_id" : "Programming",
"children" : [
"Databases",
"Languages"
],
"parent" : "books"
},{
"_id" : "books",
"children" : [
"Programming"
],
"parent" : null
}
];
var i, len, temp, top_level, id, parent, hierarchical, nodePendingObj, doc, _id, _parent, _children;
i = 0;
top_level = [];
temp = {};
obj = {};
nodePendingObj = {};
_id = '_id';
_parent = 'parent';
_children = 'children';
_.each(documents, function(doc) {
id = doc['_id'];
parent = doc[_parent];
temp[id] = doc;
if (parent === undefined || parent === null) {
obj["name"] = id;
obj["nodes"] = doc[_children];
top_level.push(obj);
}
else {
if (temp[parent] !== undefined) {
if (temp[parent][_children] === undefined) {
temp[parent][_children] = [];
}
var o = {};
o["name"] = id;
if (doc[_children].length !== 0) o["nodes"] = doc[_children];
temp[parent][_children].push(o);
} else {
if (nodePendingObj[parent] === undefined) {
nodePendingObj[parent] = [];
}
var o = {};
o["name"] = id;
if (doc[_children].length !== 0) o["nodes"] = doc[_children];
nodePendingObj[parent].push(o);
}
delete doc[_parent];
}
if (nodePendingObj[id] !== undefined) {
var len = nodePendingObj[id].length;
if (doc[_children] === undefined) {
doc[_children] = [];
}
while (len-- > 0) {
doc[_children].push(nodePendingObj[id].shift());
}
}
});
if (top_level.length === 1) {
hierarchical = top_level[0];
} else if (top_level.length > 1) {
hierarchical = {};
hierarchical[_children] = top_level;
} else {
hierarchical = {};
}
pre.innerHTML = JSON.stringify(hierarchical, null, 4);
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<pre id="pre"></pre>