How do I flatten a (forest of) trees? - javascript

I have a forest of trees of arbitrary height, more or less like this:
let data = [
{ "id": 2, "name": "AAA", "parent_id": null, "short_name": "A" },
{
"id": 10, "name": "BBB", "parent_id": null, "short_name": "B", "children": [
{
"id": 3, "name": "CCC", "parent_id": 10, "short_name": "C", "children": [
{ "id": 6, "name": "DDD", "parent_id": 3, "short_name": "D" },
{ "id": 5, "name": "EEE", "parent_id": 3, "short_name": "E" }
]
},
{
"id": 4, "name": "FFF", "parent_id": 10, "short_name": "F", "children": [
{ "id": 7, "name": "GGG", "parent_id": 4, "short_name": "G" },
{ "id": 8, "name": "HHH", "parent_id": 4, "short_name": "H" }
]
}]
}
];
And I'm trying to produce a representation of all the root-to-leaves paths, something like this
[
[
{
"id": 2,
"name": "AAA"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 3,
"name": "C"
},
{
"id": 6,
"name": "DDD"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 3,
"name": "C"
},
{
"id": 5,
"name": "EEE"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 4,
"name": "F"
},
{
"id": 7,
"name": "GGG"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 4,
"name": "F"
},
{
"id": 8,
"name": "HHH"
}
]
]
So I wrote the following code:
function flattenTree(node, path = []) {
if (node.children) {
return node.children.map(child => flattenTree(child, [...path, child]));
} else {
let prefix = path.slice(0, path.length - 1).map(n => ({ id: n.id, name: n.short_name }));
let last = path[path.length - 1];
return [...prefix, { id: last.id, name: last.name } ];
}
}
let paths = data.map(n => flattenTree(n, [n]));
but paths comes out with extra nesting, like this:
[
[
{
"id": 2,
"name": "AAA"
}
],
[
[
[
{
"id": 10,
"name": "B"
},
{
"id": 3,
"name": "C"
},
{
"id": 6,
"name": "DDD"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 3,
"name": "C"
},
{
"id": 5,
"name": "EEE"
}
]
],
[
[
{
"id": 10,
"name": "B"
},
{
"id": 4,
"name": "F"
},
{
"id": 7,
"name": "GGG"
}
],
[
{
"id": 10,
"name": "B"
},
{
"id": 4,
"name": "F"
},
{
"id": 8,
"name": "HHH"
}
]
]
]
]
I lost count of the many ways in which I tried to fix this, but it does look like the algorithm should not produce the extra nesting -- or my eyes are just so crossed by now that I couldn't see my mistake if someone stuck their finger on it.
Can someone help? Feel free to peruse this JSFiddle https://jsfiddle.net/png7x9bh/66/


The extra nestings are created by map. map just wraps the results into an array and returns them, it doesn't care if it is called on child nodes or not. Use reduce and just concat (or push, whatever suits your performance) the results into the first level array directly:
let data = [{"id":2,"name":"AAA","parent_id":null,"short_name":"A"},{"id":10,"name":"BBB","parent_id":null,"short_name":"B","children":[{"id":3,"name":"CCC","parent_id":10,"short_name":"C","children":[{"id":6,"name":"DDD","parent_id":3,"short_name":"D"},{"id":5,"name":"EEE","parent_id":3,"short_name":"E"}]},{"id":4,"name":"FFF","parent_id":10,"short_name":"F","children":[{"id":7,"name":"GGG","parent_id":4,"short_name":"G"},{"id":8,"name":"HHH","parent_id":4,"short_name":"H"}]}]}];
function flattenTree(node, path = []) {
let pathCopy = Array.from(path);
pathCopy.push({id: node.id, name: node.name});
if(node.children) {
return node.children.reduce((acc, child) => acc.concat(flattenTree(child, pathCopy)), []);
}
return [pathCopy];
}
let result = data.reduce((result, node) => result.concat(flattenTree(node)), []);
console.log(JSON.stringify(result, null, 3));

Related

Transformation of nested object

I am new to JavaScript and Node JS
want to transform the following nested object with student
Data:
[{
"id": 1,
"name": "A",
"children": [{
"id": 2,
"name": "B",
"children": [{
"id": 3,
"name": "C"
},
{
"id": 4,
"name": "D"
}
]
}]
}]
to
Expected:
[{
"student": {
"id": 1,
"name": "A"
},
"children": [{
"student": {
"id": 2,
"name": "B"
},
"children": [{
"student": {
"id": 3,
"name": "C"
}
},
{
"student": {
"id": 4,
"name": "D"
}
}
]
}]
}]

I guess you are seeking a solution for an array with multiple student objects. So you can use the map method to modify them.
const original = [{
"id": 1,
"name": "A",
"children": [{
"id": 2,
"name": "B",
"children": [{
"id": 3,
"name": "C"
},
{
"id": 4,
"name": "D"
}
]
}]
}]
const modified = original.map(stu => {
return {
student: {
id: stu.id,
name: stu.name,
},
children: stu.children
}
})

Fetch object id with Javascript

I have the following array of objects:
[
{
"id": 97,
"name": "Jon",
"technologies": [
{
"id": 6,
"name": "React"
},
{
"id": 7,
"name": "Messageria"
}
]
},
{
"id": 98,
"name": "Doe",
"technologies": [
{
"id": 2,
"name": "Javascript"
},
{
"id": 6,
"name": "React"
}
]
},
{
"id": 99,
"name": "Mark",
"technologies": [
{
"id": 8,
"name": "PHP"
},
{
"id": 9,
"name": "Laravel"
}
]
}
]
How could I filter this array and return only developers who have, for example, technology with id 6?
The return I need is only developers who have a relationship with technology id 6, however I need other related technologies to also appear to the developer.
I know that through the find method it is possible to do this, but I don't know how to implement it.
const result = developers.find(dev => dev.technologies ?);
What would be the correct form?

You can use filter with some array operations for this task. Something like this:
persons.filter(person => person.technologies.some(tech => tech.id == 6))

This will return details of person with technology id 6:
persons = [
{
"id": 97,
"name": "Jon",
"technologies": [
{
"id": 6,
"name": "React"
},
{
"id": 7,
"name": "Messageria"
}
]
},
{
"id": 98,
"name": "Doe",
"technologies": [
{
"id": 2,
"name": "Javascript"
},
{
"id": 6,
"name": "React"
}
]
},
{
"id": 99,
"name": "Mark",
"technologies": [
{
"id": 8,
"name": "PHP"
},
{
"id": 9,
"name": "Laravel"
}
]
}
]
persons.filter(person => person.technologies.find(tech => tech.id == 6))

You need to use some for finding whether element exist with specific id or not:
const data = [
{
"id": 97,
"name": "Jon",
"technologies": [
{
"id": 6,
"name": "React"
},
{
"id": 7,
"name": "Messageria"
}
]
},
{
"id": 98,
"name": "Doe",
"technologies": [
{
"id": 2,
"name": "Javascript"
},
{
"id": 6,
"name": "React"
}
]
},
{
"id": 99,
"name": "Mark",
"technologies": [
{
"id": 8,
"name": "PHP"
},
{
"id": 9,
"name": "Laravel"
}
]
}
]
const myFilteredData = data.filter(test => test.technologies.some(data => data.id===6));
console.log(
myFilteredData
)

How to filter through children of array of objects and then return parent with updated children?

I'm trying to filter through an array of objects it's children then update the children and return the parent with updated children.
Example array of objects:
[
{
"id": 1,
"name": "group1",
"users": [
{
"id": 1,
"name": "Mike"
},
{
"id": 2,
"name": "Steve"
},
{
"id": 3,
"name": "John"
}
]
},
{
"id": 2,
"name": "group2",
"users": [
{
"id": 4,
"name": "Phill"
},
{
"id": 5,
"name": "Joe"
},
{
"id": 6,
"name": "Dominik"
}
]
}
]
I've got an input in React where someone can type in a name of an user, then i'd like to only show the users with that name while keeping the group that they're in.
For example, if the input is 'Mike' I would like the result to be:
[
{
"id": 1,
"name": "group1",
"users": [
{
"id": 1,
"name": "Mike"
}
]
},
{
"id": 2,
"name": "group2",
"users": []
}
]

You can use map() and filter() to do that.
let arr = [ { "id": 1, "name": "group1", "users": [ { "id": 1, "name": "Mike" }, { "id": 2, "name": "Steve" }, { "id": 3, "name": "John" } ] }, { "id": 2, "name": "group2", "users": [ { "id": 4, "name": "Phill" }, { "id": 5, "name": "Joe" }, { "id": 6, "name": "Dominik" } ] } ];
function filterUsers(arr, name) {
return arr.map(obj => {
return {
...obj,
"users": obj.users.filter(user => user.name === name)
};
});
}
console.log(filterUsers(arr, "Mike"));

Using angularjs forEach loops

I am getting this type of json in my $scope of angularjs:
$scope.someStuff = {
"id": 2,
"service": "bike",
"min": "22",
"per": "100",
"tax": "1",
"categoryservices": [
{
"id": 32,
"category": {
"id": 1,
"name": "software"
}
},
{
"id": 33,
"category": {
"id": 2,
"name": "hardware"
}
},
{
"id": 34,
"category": {
"id": 3,
"name": "waterwash"
}
}
]
}
I want to use angularjs forEach loop and i want to get only category name,
My expected output:
[{"name":"software"}, {"name":"hardware"}, {"name":"waterwash"}]

You can use Array.map()
The map() method creates a new array with the results of calling a provided function on every element in the calling array.
$scope.someStuff.categoryservices.map((x) => { return { name: x.category.name}})
var obj = {
"id": 2,
"service": "bike",
"min": "22",
"per": "100",
"tax": "1",
"categoryservices": [{
"id": 32,
"category": {
"id": 1,
"name": "software"
}
},
{
"id": 33,
"category": {
"id": 2,
"name": "hardware"
}
},
{
"id": 34,
"category": {
"id": 3,
"name": "waterwash"
}
}
]
};
console.log(obj.categoryservices.map((x) => {
return {
name: x.category.name
}
}))

You can use map method by passing a callback function as parameter.
const someStuff = { "id": 2, "service": "bike", "min": "22", "per": "100", "tax": "1", "categoryservices": [ { "id": 32, "category": { "id": 1, "name": "software" } }, { "id": 33, "category": { "id": 2, "name": "hardware" } }, { "id": 34, "category": { "id": 3, "name": "waterwash" } } ] }
let array = someStuff.categoryservices.map(function({category}){
return {'name' : category.name}
});
console.log(array);

How to collect value in javascript?

I have an array like this in Javascript. Something like this
[
{
"id": 1,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
}
]
},
{
"id": 2,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 13,
"name": "Snack",
"label": "Snack"
}
]
},
{
"id": 3,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 14,
"name": "Petrol",
"label": "Petrol"
}
]
}
]
I want to collect data and grouping data facilities of the array in Javascript, something like this.
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 13,
"name": "Snack",
"label": "Snack"
},
{
"id": 14,
"name": "Petrol",
"label": "Petrol"
}
]
So, basically, group by facilities. I just don't know how to handle the grouping of similar facilities values.

Assuming the facility ids are unique:
const facilities = input.reduce((memo, entry) => {
entry.facilities.forEach((f) => {
if (!memo.some((m) => m.id === f.id)) {
memo.push(f)
}
})
return memo
}, [])

You can iterate through all rows and collect (id, entity) map.
Index map allows us to not search already collected entities every time.
Then you can convert it to an array with object keys mapping.
let input = [
{"id": 1, "facilities": [{"id": 10, "name": "Wifi", "label": "Wifi"}, {"id": 12, "name": "Toll", "label": "Toll"} ] },
{"id": 2, "facilities": [{"id": 10, "name": "Wifi", "label": "Wifi"}, {"id": 12, "name": "Toll", "label": "Toll"}, {"id": 13, "name": "Snack", "label": "Snack"} ] },
{"id": 3, "facilities": [{"id": 10, "name": "Wifi", "label": "Wifi"}, {"id": 12, "name": "Toll", "label": "Toll"}, {"id": 14, "name": "Petrol", "label": "Petrol"} ] }
];
let index = input.reduce((res, row) => {
row.facilities.forEach(f => res[f.id] = f);
return res;
}, {});
let result = Object.keys(index).map(id => index[id]);
console.log({facilities: result});

You could use a Set for flagging inserted objects with the given id.
var data = [{ id: 1, facilities: [{ id: 10, name: "Wifi", label: "Wifi" }, { id: 12, name: "Toll", label: "Toll" }] }, { id: 2, facilities: [{ id: 10, name: "Wifi", label: "Wifi" }, { id: 12, name: "Toll", label: "Toll" }, { id: 13, name: "Snack", label: "Snack" }] }, { id: 3, facilities: [{ id: 10, name: "Wifi", label: "Wifi" }, { id: 12, name: "Toll", label: "Toll" }, { id: 14, name: "Petrol", label: "Petrol" }] }],
grouped = data.reduce(
(s => (r, a) => (a.facilities.forEach(b => !s.has(b.id) && s.add(b.id) && r.push(b)), r))(new Set),
[]
);
console.log(grouped);
.as-console-wrapper { max-height: 100% !important; top: 0; }

The solution using Array.prototype.reduce() and Set object:
var data = [{"id": 1,"facilities": [{"id": 10,"name": "Wifi","label": "Wifi"},{"id": 12,"name": "Toll","label": "Toll"}]},{"id": 2,"facilities": [{"id": 10,"name": "Wifi","label": "Wifi"},{"id": 12,"name": "Toll","label": "Toll"},{"id": 13,"name": "Snack","label": "Snack"}]},{"id": 3,"facilities": [{"id": 10,"name": "Wifi","label": "Wifi"},{"id": 12,"name": "Toll","label": "Toll"},{"id": 14,"name": "Petrol","label": "Petrol"}]}
];
var ids = new Set(),
result = data.reduce(function (r, o) {
o.facilities.forEach(function(v) { // iterating through nested `facilities`
if (!ids.has(v.id)) r.facilities.push(v);
ids.add(v.id); // saving only items with unique `id`
});
return r;
}, {facilities: []});
console.log(result);

const input = [
{
"id": 1,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
}
]
},
{
"id": 2,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 13,
"name": "Snack",
"label": "Snack"
}
]
},
{
"id": 3,
"facilities": [
{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 14,
"name": "Petrol",
"label": "Petrol"
}
]
}
]
const result = []
const idx = []
for (const item of input) {
for (const facilityItem of item.facilities) {
if (!idx.includes(facilityItem.id)) {
idx.push(facilityItem.id)
result.push(facilityItem)
}
}
}
console.log(result)

A very simple and easily understood approach.
const data = [{
"id": 1,
"facilities": [{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
}
]
},
{
"id": 2,
"facilities": [{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 13,
"name": "Snack",
"label": "Snack"
}
]
},
{
"id": 2,
"facilities": [{
"id": 10,
"name": "Wifi",
"label": "Wifi"
},
{
"id": 12,
"name": "Toll",
"label": "Toll"
},
{
"id": 14,
"name": "Petrol",
"label": "Petrol"
}
]
}
];
let o = {};
let result = [];
data.forEach((d) => {
d.facilities.forEach((f) => {
o[f.id] = f;
});
});
for (let r in o) {
result.push(o[r]);
}
console.log(result);

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