Develop Reference

Node Js how to fetch data from database in an hierarchical way

I'm writing a back code using NodeJs to fetch some data from backend, I want dataBase data to be like this
like this:
data = [{
name: "Admin",
id: '1',
children: [
{ name: "Admin", id: "1" },
{ name: "groupe1", id: "2" },
{
name: "groupe2", id: "1455", children: [
{ name: "groupe2", id: "1455" },
{ name: "gro", id: "5444" },
{ name: "hhrr", id: "45" }
]
}
]
}]
the idea is simple we have a list of group each group has a parent I want to display all the groups list in an hierarchical way the top one of the tree is done
Some groups are parents and groups in the same time and some others are only groups if the group is not parent we add an object with its name and ID in the array of children of his parent
if this groups is a parent that's mean it has children we add an object with its ID and name in the array of children of his parents, and we add property children for the object which is array named children with for the first time an object with the name and the id of the group etc...
i tryed to do this but it did not work
const getParentsByType = async ({ name, _id }) => {
let parentResult = [
{
id: _id,
name: name,
children: [
{
id: _id,
name: name,
},
],
},
];
parentResult= await findParent(_id, parentResult[0].children, 0);
return parentResult;
};
const findParent = async (parentId, parentResult, itemPos) => {
let children = await Models.GroupModel.find({ parent: parentId, status: true }).select('name _id');
for (let i = 0; i < children.length; i++) {
let childrenList = await Models.GroupModel.find({ parent: children[i]._id, status: true }).select('name _id');
if (childrenList.length != 0) {
parentResult.push(buildParentWithChild(children[i]._id, children[i].name));
findParent(children[i]._id,parentResult.children[i],itemPos++)
} else {
parentResult.push(buildParent(children[i]._id, children[i].name));
}
}
return parentResult
};
and this the model of the data base
const Group = mongoose.Schema({
name: {
type: String,
required: true,
},
status: {
type: Boolean,
required: true,
},
parent: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Group',
},
});
i had two days trying to resolve tis but with no result
i need some helps and Thank you

Try parsing your returned data. It validates your data as objects i dont see any problem with your function regardless i still have no idea what format your a trying to build.
let children = JSON.parse(JSON.stringify(await Models.GroupModel.find({ parent: parentId, status: true }).select('name _id')));
let childrenList = JSON.parse(JSON.stringify(await Models.GroupModel.find({ parent: children[i]._id, status: true }).select('name _id')));

If I understand you right, you want to convert the array returned by Models.GroupModel.find, and which looks like
var dbresult = [
{_id: "1", parent: null, name: "one"},
{_id: "2", parent: "1", name: "two"}
];
into a hierarchical structure. This can be done with a function that adds all children of a given parent p, including, recursively, their children. Like the following:
function children(p) {
var result = [];
for (r of dbresult) if (r.parent === p) {
var row = {_id: r._id, name: r.name};
var chld = children(r._id);
if (chld.length > 0) row.children = chld;
result.push(row);
}
return result;
}
console.log(JSON.stringify(children(null)));
Note that this approach requires only one database access (to fill the dbresult) and is therefore probably faster than your findParent function.

Javascript - Update object in array by id and move it to the first index

I have this array:
const chats = [
{ id: "chat-1", msg: { text: "World", date: (a date) } },
{ id: "chat-2", msg: { text: "Hello", date: (a date) } },
];
After receiving updates from my database, I receive this object:
// The second chat with update data
{ id: "chat-2", msg: { text: "Bye", date: (a date) } },
How can I (using ES6) replace the chat object from the original chats array and move it to the first index?
For now, I am doing this, but I am looking for a fastest way (smaller O)
// Get the modified chat
const modifiedChat = response.data;
// Search the modified chat in the chats array by id
const chatIndex = chats.findIndex(
(chat) => chat.id === modifiedChat.id
);
// Finally, using spread syntax, add the updated chat to the head of our current chats array
chats = [
modifiedChat,
...chats.slice(0, chatIndex),
...chats.slice(chatIndex + 1),
];

You can do the following,
const chats = [
{ id: "chat-1", msg: { text: "World", date: '' } },
{ id: "chat-2", msg: { text: "Hello", date: '' } },
];
const modifiedChat = { id: "chat-2", msg: { text: "Bye", date: '' } };
const newChats = [modifiedChat, ...chats.filter(item => item.id !== modifiedChat.id)];
console.log(newChats);

You can do something similar to how LRU cache works. You can now access every chat in O(1)

Taking JSON values in a response and mapping them to a state object with keys?

[Noob to Javascript and React] I am using an API that returns an object with values like this. AAPL, AMZN, FB, GOOGL, can be anything based on the function's string array input.
{
AAPL: { price: 329.99 },
AMZN: { price: 2563.05 },
FB: { price: 239.93 },
GOOGL: { price: 1469.12 }
}
How could I consider dynamically mapping a response like this into a state object like this? The id property doesn't exist, it needs to be created.
state = {
stocks: [ { id: 1, name: 'AAPL', price: 329.99 }, { id: 2, name: 'AMZN', price: 2563.05 }, ...]
}
I'm able to successfully print the stock names and their prices separately but I am having trouble figuring out how I could wire them into a state object like what's above.
function getCurrentPriceOfBatchStocks(_stocks) {
iex
.symbols(_stocks)
.price()
.then(res => {
console.log(typeof res);
console.log(res);
console.log(Object.keys(res));
console.log(Object.values(res));
});
}

Not sure where you're getting id from, so I'm using idx as an example.
const stocks = Object.keys(resp).map((key, idx) => ({ id: idx + 1, name: key, price: resp[key] }))

Here is an implementation. With Object.entries, you get an array with an array of [key, value] of your original object. And you can map this array to a different format.
You can check the result with the Run code snippet button.
let st = {
AAPL: { price: 329.99 },
AMZN: { price: 2563.05 },
FB: { price: 239.93 },
GOOGL: { price: 1469.12 }
}
let stocks = Object.entries(st).map(([key, value], index) => ({id: index + 1, name: key, price: value.price}))
console.log(stocks)

const res={
AAPL: { price: 329.99 },
AMZN: { price: 2563.05 },
FB: { price: 239.93 },
GOOGL: { price: 1469.12 }
}
console.log(Object.entries(res).map((entry,index)=>{
return {
id:index+1,
name:entry[0],
...entry[1]
}
}));

How to return an array of objects in GraphQL, possibly using the same endpoint as the one that returns a single object?

I am making a GraphQL API where I would be able to retrieve a car object by its id or retrieve all the cars when no parameter is provided.
Using the code below, I am successfully able to retrieve a single car object by supplying id as a parameter.
However, in the case where I would expect an array of objects i.e. when I supply no parameter at all, I get no result on GraphiQL.
schema.js
let cars = [
{ name: "Honda", id: "1" },
{ name: "Toyota", id: "2" },
{ name: "BMW", id: "3" }
];
const CarType = new GraphQLObjectType({
name: "Car",
fields: () => ({
id: { type: GraphQLString },
name: { type: GraphQLString }
})
});
const RootQuery = new GraphQLObjectType({
name: "RootQueryType",
fields: {
cars: {
type: CarType,
args: {
id: { type: GraphQLString }
},
resolve(parent, args) {
if (args.id) {
console.log(cars.find(car => car.id == args.id));
return cars.find(car => car.id == args.id);
}
console.log(cars);
//***Problem Here***
return cars;
}
}
}
});
Test queries and their respective results:
Query 1
{
cars(id:"1"){
name
}
}
Query 1 Response (Success)
{
"data": {
"cars": {
"name": "Honda"
}
}
}
Query 2
{
cars{
name
}
}
Query 2 Response (Fail)
{
"data": {
"cars": {
"name": null
}
}
}
Any help would be much appreciated.

A Car and a List of Cars are effectively two separate types. A field cannot resolve to a single Car object one time, and an array of Car object another.
Your query is returning null for the name because you told it the cars field would resolve to a single object, but it resolved to an array instead. As a result, it's looking for a property called name on the array object and since one doesn't exist, it's returning null.
You can handle this in a couple of different ways. To keep things to one query, you can use filter instead of find and change the type of your query to a List.
cars: {
type: new GraphQLList(CarType), // note the change here
args: {
id: {
type: GraphQLString
},
},
resolve: (parent, args) => {
if (args.id) {
return cars.filter(car => car.id === args.id);
}
return cars;
}
}
Alternatively, you could split this into two separate queries:
cars: {
type: new GraphQLList(CarType),
resolve: (parent, args) => cars,
},
car: {
type: CarType,
args: {
id: {
// example of using GraphQLNonNull to make the id required
type: new GraphQLNonNull(GraphQLString)
},
},
resolve: (parent, args) => cars.find(car => car.id === args.id),
}
Check the docs for more examples and options.

Mongoose, sort query by populated field

As far as I know, it's possible to sort populated docs with Mongoose (source).
I'm searching for a way to sort a query by one or more populated fields.
Consider this two Mongoose schemas :
var Wizard = new Schema({
name : { type: String }
, spells : { [{ type: Schema.ObjectId, ref: 'Spell' }] }
});
var Spell = new Schema({
name : { type: String }
, damages : { type: Number }
});
Sample JSON:
[{
name: 'Gandalf',
spells: [{
name: 'Fireball',
damages: 20
}]
}, {
name: 'Saruman',
spells: [{
name: 'Frozenball',
damages: 10
}]
}, {
name: 'Radagast',
spells: [{
name: 'Lightball',
damages: 15
}]
}]
I would like to sort those wizards by their spell damages, using something like :
WizardModel
.find({})
.populate('spells', myfields, myconditions, { sort: [['damages', 'asc']] })
// Should return in the right order: Saruman, Radagast, Gandalf
I'm actually doing those sorts by hands after querying and would like to optimize that.

You can explicitly specify only required parameters of populate method:
WizardModel
.find({})
.populate({path: 'spells', options: { sort: [['damages', 'asc']] }})
Have a look at http://mongoosejs.com/docs/api.html#document_Document-populate
Here is an example from a link above.
doc
.populate('company')
.populate({
path: 'notes',
match: /airline/,
select: 'text',
model: 'modelName'
options: opts
}, function (err, user) {
assert(doc._id == user._id) // the document itself is passed
})

Even though this is rather an old post, I'd like to share a solution through the MongoDB aggregation lookup pipeline
The important part is this:
{
$lookup: {
from: 'spells',
localField: 'spells',
foreignField:'_id',
as: 'spells'
}
},
{
$project: {
_id: 1,
name: 1,
// project the values from damages in the spells array in a new array called damages
damages: '$spells.damages',
spells: {
name: 1,
damages: 1
}
}
},
// take the maximum damage from the damages array
{
$project: {
_id: 1,
spells: 1,
name: 1,
maxDamage: {$max: '$damages'}
}
},
// do the sorting
{
$sort: {'maxDamage' : -1}
}
Find below a complete example
'use strict';
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
mongoose.connect('mongodb://localhost/lotr');
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', () => {
let SpellSchema = new Schema({
name : { type: String },
damages : { type: Number }
});
let Spell = mongoose.model('Spell', SpellSchema);
let WizardSchema = new Schema({
name: { type: String },
spells: [{ type: Schema.Types.ObjectId, ref: 'Spell' }]
});
let Wizard = mongoose.model('Wizard', WizardSchema);
let fireball = new Spell({
name: 'Fireball',
damages: 20
});
let frozenball = new Spell({
name: 'Frozenball',
damages: 10
});
let lightball = new Spell({
name: 'Lightball',
damages: 15
});
let spells = [fireball, frozenball, lightball];
let wizards = [{
name: 'Gandalf',
spells:[fireball]
}, {
name: 'Saruman',
spells:[frozenball]
}, {
name: 'Radagast',
spells:[lightball]
}];
let aggregation = [
{
$match: {}
},
// find all spells in the spells collection related to wizards and fill populate into wizards.spells
{
$lookup: {
from: 'spells',
localField: 'spells',
foreignField:'_id',
as: 'spells'
}
},
{
$project: {
_id: 1,
name: 1,
// project the values from damages in the spells array in a new array called damages
damages: '$spells.damages',
spells: {
name: 1,
damages: 1
}
}
},
// take the maximum damage from the damages array
{
$project: {
_id: 1,
spells: 1,
name: 1,
maxDamage: {$max: '$damages'}
}
},
// do the sorting
{
$sort: {'maxDamage' : -1}
}
];
Spell.create(spells, (err, spells) => {
if (err) throw(err);
else {
Wizard.create(wizards, (err, wizards) =>{
if (err) throw(err);
else {
Wizard.aggregate(aggregation)
.exec((err, models) => {
if (err) throw(err);
else {
console.log(models[0]); // eslint-disable-line
console.log(models[1]); // eslint-disable-line
console.log(models[2]); // eslint-disable-line
Wizard.remove().exec(() => {
Spell.remove().exec(() => {
process.exit(0);
});
});
}
});
}
});
}
});
});

here's the sample of mongoose doc.
var PersonSchema = new Schema({
name: String,
band: String
});
var BandSchema = new Schema({
name: String
});
BandSchema.virtual('members', {
ref: 'Person', // The model to use
localField: 'name', // Find people where `localField`
foreignField: 'band', // is equal to `foreignField`
// If `justOne` is true, 'members' will be a single doc as opposed to
// an array. `justOne` is false by default.
justOne: false,
options: { sort: { name: -1 }, limit: 5 }
});