Efficient way of writing child of parents in javascript - javascript

var array = [
{id: 1, name: "Father", parent_id: null},
{id: 2, name: "Child", parent_id: 1},
{id: 3, name: "Child", parent_id: 1},
{id: 4, name: "ChildChild", parent_id: 2},
{id: 5, name: "ChildChildChild", parent_id: 4}
]
for(var i in array){
if(array[i].parent_id == null){
console.log(array[i].name);
} else {
for(var j in array){
if(array[i].parent_id == array[j].id && array[j].parent_id == null){
console.log(">" + array[i].name);
for(var x in array){
if(array[i].id == array[x].parent_id){
console.log(">>" + array[x].name);
}
}
}
}
}
}
Output:
Father
>Child
>>ChildChild
>Child
I have this array which has id, name and parent_id. Right now it is fixed but it could have multiple arrays and can be nested for n amount of times.
What I am doing here is iterating through each array and trying to find which are the parents and which one is the child.
I want to know if there is a more efficient way to write this code. For instance, I added a fifth id but that would require another for loop and so on. The output would be the same just a printed out tree.

You can use a Map to key your nodes by id, and then use recursion to traverse them in depth first order:
var array = [{id: 1, name: "Father", parent_id: null},{id: 2, name: "Child", parent_id: 1},{id: 3, name: "Child", parent_id: 1},{id: 4, name: "ChildChild", parent_id: 2},{id: 5, name: "ChildChildChild", parent_id: 4}];
let map = new Map(array.map(({id}) => [id, []])).set(null, []);
array.forEach(node => map.get(node.parent_id).push(node));
function dfs(nodes, indent="") {
for (let node of nodes) {
console.log(indent + node.name);
dfs(map.get(node.id), indent+">");
}
}
dfs(map.get(null));

You could create a tree and then make the output.
const
print = ({ name, children = [] }) => {
console.log(name)
children.forEach(print);
},
array = [{ id: 1, name: "Father", parent_id: null }, { id: 2, name: "Child", parent_id: 1 }, { id: 3, name: "Child", parent_id: 1 }, { id: 4, name: "ChildChild", parent_id: 2 }, { id: 5, name: "ChildChildChild", parent_id: 4 }],
tree = function (data, root) {
var t = {};
data.forEach(o => {
Object.assign(t[o.id] = t[o.id] || {}, o);
t[o.parent_id] = t[o.parent_id] || {};
t[o.parent_id].children = t[o.parent_id].children || [];
t[o.parent_id].children.push(t[o.id]);
});
return t[root].children;
}(array, null);
tree.forEach(print);
console.log(tree);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Related

array grouping conversion key start_section to end_section

Let's say I have below array :
[{id: 1, name: "header"},{id: 2, name: "start_section"},
{id: 3, name: "input"}, {id: 5, name: "image"},
{id: 6, name: "end_section"}, {id: 7, name: "header"},
{id: 8, name: "start_section"}, {id: 9, name: "input"},
{id: 10, name: "date"}, {id: 11, name: "end_section"},
]
I want this :
[{
id: 1,
name: "header"
}, {
id: 2,
name: "section",
child: [{
{
id: 3,
name: "input"
},
{
id: 5,
name: "image"
},
}],
}, {
id: 7,
name: "header"
}, {
id: 8,
name: "section",
child: [{
{
id: 9,
name: "input"
},
{
id: 10,
name: "date"
},
}]
}]
if I find start_section and end_section then it will form a new object , How do I change the array by grouping by the key specified in the example above in javascript?
If I get it right, you want something like this? It's simple approach with for loop and some flags:
const arr = [{id: 1, name: "header"},{id: 2, name: "start_section"},
{id: 3, name: "input"}, {id: 5, name: "image"},
{id: 6, name: "end_section"}, {id: 7, name: "header"},
{id: 8, name: "start_section"}, {id: 9, name: "input"},
{id: 10, name: "date"}, {id: 11, name: "end_section"},
];
// Set final array
let finalArray = [];
// Set sub object for groups (Childs)
let subObj = {};
// Flag for sub section stuff
let inSubSection = false;
// Loop array
for(let i = 0; i < arr.length; i++) {
if(arr[i].name === "end_section") {
// If we have end_section
// Set flag off
inSubSection = false;
// Push sub object to final array
finalArray.push(subObj);
} else if(arr[i].name === "start_section") {
// If we get start_section
// Set flag on
inSubSection = true;
// Set new sub object, set childs array in it
subObj = {
id: arr[i].id,
name: "section",
child: []
};
} else if(inSubSection) {
// If we have active flag (true)
// Push child to section array
subObj.child.push({
id: arr[i].id,
name: arr[i].name
});
} else {
// Everything else push straight to final array
finalArray.push(arr[i]);
}
}
// Log
console.log(finalArray);
you can Array.reduce function
let array = [{id: 1, name: "header"},{id: 2, name: "start_section"},
{id: 3, name: "input"}, {id: 5, name: "image"},
{id: 6, name: "end_section"}, {id: 7, name: "header"},
{id: 8, name: "start_section"}, {id: 9, name: "input"},
{id: 10, name: "date"}, {id: 11, name: "end_section"},
]
let outPut = array.reduce( (acc, cur, i, arr) => {
if (cur.name == "start_section") {
//find the end element
let endIndex = arr.slice(i).findIndex( e => e.name == "end_section") + i ;
//splice the child elements from base array
let child = arr.splice(i + 1, endIndex - 1 );
//remove last element that has "end_section"
child.splice(-1);
//append child
cur.child = child;
//sert the name as "section"
cur.name = "section";
}
//add to accumulator
acc.push(cur);
return acc;
}, []);
console.log(outPut);

Turn array of objects into structured object? [duplicate]

I am working on a Nodejs project. I have to create a function which takes an object (a child category) like:
{
id: 65,
name: 'Outdoor',
parent_id: 2
}
Now I want my function to check for the parent category by using parent_id from database and return an array/object like this:
{
id: 2,
name: 'Furniture',
parent: {
id: 1,
name: 'Residential',
parent: {
id: ...,
name: ...,
parent: {
and so on..
}
}
}
}
This is what I have done so far:
* _get_category_parents(category, _array) {
if(_array === undefined) _array = []
if( category.parent_id !== 0 ) {
const c_parent = yield this.Database.from('categories').where('id', '=', category.parent_id)
_array.push({id: c_parent[0].id, name: c_parent[0].name})
yield this._get_category_parents(c_parent[0], _array)
}
return _array
}
And calling this function like this:
const parents = yield this._get_category_parents(category)
This returns me an array of parents like this:
[
{
"id": 2,
"name": "Furniture"
},
{
"id": 1,
"name": "Residential"
}
]
I want Residential object to be appended in Furniture's parent node.
I have spent too much time on this but not getting what I want. Any help would be deeply appreciated.
What you want to think about is a recursive solution.
Since you're calling a database, it's probably unlikely, but if the lookup by id is synchronous, you might do it with code something like the following (note that I'm faking a db here):
const getHierarchy = (lookup, child) => {
const {id, name, parent_id} = lookup(child) ||
{id: null, name: null, parent_id: 0}
return parent_id == 0
? {id, name, parent_id}
: {...{id, name}, ...{parent: getHierarchy(lookup, {parent_id})}}
}
const items = [
{id: 1, name: 'Residential', parent_id: 5},
{id: 2, name: 'Furniture', parent_id: 1},
{id: 3, name: 'Other', parent_id: 0},
{id: 4, name: 'FooBar', parent_id: 3},
{id: 5, name: 'Stuff', parent_id: 0}
]
const lookup = child => items.find(item => item.id == child.parent_id)
const item = {id: 65, name: 'Outdoor', parent_id: 2}
console.log(getHierarchy(lookup, item))
You would have to write an appropriate lookup function, presumably using this.Database.from(...). You might also want to simplified version that bakes in your lookup function, in which case, you might write
const getAncestry = (item) => getHierarchy(lookup, item)
If, as seems more likely, your lookup is asynchronous, then that will affect getHierarchy and how you call it. Here's one possibility:
const getHierarchy = async (lookup, child) => {
const {id, name, parent_id} = await lookup(child) ||
{id: null, name: null, parent_id: 0}
return parent_id == 0
? {id, name, parent_id}
: {...{id, name}, ...{parent: await getHierarchy(lookup, {parent_id})}}
}
const items = [
{id: 1, name: 'Residential', parent_id: 5},
{id: 2, name: 'Furniture', parent_id: 1},
{id: 3, name: 'Other', parent_id: 0},
{id: 4, name: 'FooBar', parent_id: 3},
{id: 5, name: 'Stuff', parent_id: 0}
]
const lookup = async child => new Promise(
(resolve, reject) => setTimeout(
() => resolve(items.find(item => item.id == child.parent_id)),
1000
)
)
const getAncestry = async item => getHierarchy(lookup, item)
const item = {id: 65, name: 'Outdoor', parent_id: 2}
getAncestry(item).then(console.log)
Note the change in how you call the function. You need to call .then() on the resulting promise to get any useful behavior.

compare two arrays in javascript and delete the object that both arrays have

I have 2 arrays:
0: {id: 2, name: "TMA"}
1: {id: 3, name: "Hibbernate"}
0: {id: 1, name: "FB.DE"}
1: {id: 2, name: "TMA"}
2: {id: 3, name: "Hibbernate"}
3: {id: 4, name: "Event.it A"}
4: {id: 5, name: "Projket 2"}
5: {id: 6, name: "Projekt 1"}
I want to compare them and delete the objects with the id 2 and 3 cause both arrays have them and thats the similarity.
This is my Code so far:
const projectListOutput = projectsOfPersonArray.filter(project => data.includes(project));
console.log(projectListOutput);
But every time i run this projectListOutput is empty.
When using includes dont compare objects, Just build data as array of strings. Remaining code is similar to what you have.
arr1 = [
{ id: 2, name: "TMA" },
{ id: 3, name: "Hibbernate" },
];
arr2 = [
{ id: 1, name: "FB.DE" },
{ id: 2, name: "TMA" },
{ id: 3, name: "Hibbernate" },
{ id: 4, name: "Event.it A" },
{ id: 5, name: "Projket 2" },
{ id: 6, name: "Projekt 1" },
];
const data = arr1.map(({ id }) => id);
const result = arr2.filter(({ id }) => !data.includes(id));
console.log(result);
Your data array probably does not contain the exact same object references than projectsOfPersonArray. Look at the code below:
[{ foo: 'bar' }].includes({ foo: 'bar' });
// false
Objects look equal, but they don't share the same reference (= they're not the same).
It's safer to use includes with primitive values like numbers or strings. You can for example check the ids of your objects instead of the full objects.
You compare different objects, so every object is unique.
For filtering, you need to compare all properties or use a JSON string, if the order of properties is equal.
var exclude = [{ id: 2, name: "TMA" }, { id: 3, name: "Hibbernate" }],
data = [{ id: 2, name: "TMA" }, { id: 3, name: "Hibbernate" }, { id: 1, name: "FB.DE" }, { id: 2, name: "TMA" }, { id: 3, name: "Hibbernate" }, { id: 4, name: "Event.it A" }, { id: 5, name: "Projket 2" }, { id: 6, name: "Projekt 1" }],
result = data.filter(project =>
!exclude.some(item => JSON.stringify(item) === JSON.stringify(project))
);
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
You can do something similar to the next:
const source = [{
id: 1,
name: "FB.DE"
},
{
id: 2,
name: "TMA"
},
{
id: 3,
name: "Hibbernate"
},
{
id: 4,
name: "Event.it A"
},
{
id: 5,
name: "Projket 2"
},
{
id: 6,
name: "Projekt 1"
}
]
const toRemove = [{
id: 2,
name: "TMA"
},
{
id: 3,
name: "Hibbernate"
}
]
/**create object where keys is object "id" prop, and value is true**/
const toRemoveMap = toRemove.reduce((result, item) => ({
...result,
[item.id]: true
}), {})
const result = source.filter(item => !toRemoveMap[item.id])
You can make function from it:
function removeArrayDuplicates (sourceArray, duplicatesArray, accessor) {
const toRemoveMap = duplicatesArray.reduce((result, item) => ({
...result,
[item[accessor]]: true
}), {});
return sourceArray.filter(item => !toRemoveMap[item[accessor]])
}
removeArrayDuplicates(source, toRemove, 'id')
Or even better, you can make it work with a function instead of just property accessor:
function removeDuplicates (sourceArray, duplicatesArray, accessor) {
let objectSerializer = obj => obj[accessor];
if(typeof accessor === 'function') {
objectSerializer = accessor;
}
const toRemoveMap = duplicatesArray.reduce((result, item) => ({
...result,
[objectSerializer(item)]: true
}), {});
return sourceArray.filter(item => !toRemoveMap[objectSerializer(item)])
}
removeDuplicates(source, toRemove, (obj) => JSON.stringify(obj))
This function will help you merge two sorted arrays
var arr1 = [
{ id: 2, name: 'TMA' },
{ id: 3, name: 'Hibbernate' },
]
var arr2 = [
{ id: 1, name: 'FB.DE' },
{ id: 2, name: 'TMA' },
{ id: 3, name: 'Hibbernate' },
{ id: 4, name: 'Event.it A' },
{ id: 5, name: 'Projket 2' },
]
function mergeArray(array1, array2) {
var result = []
var firstArrayLen = array1.length
var secondArrayLen = array2.length
var i = 0 // index for first array
var j = 0 // index for second array
while (i < firstArrayLen || j < secondArrayLen) {
if (i === firstArrayLen) { // first array doesn't have any other members
while (j < secondArrayLen) { // we copy rest members of first array as a result
result.push(array2[j])
j++
}
} else if (j === secondArrayLen) { // second array doesn't have any other members
while (i < firstArrayLen) { // we copy the rest members of the first array to the result array
result.push(array1[i])
i++
}
} else if (array1[i].id < array2[j].id) {
result.push(array1[i])
i++
} else if (array1[i].id > array2[j].id) {
result.push(array2[j])
j++
} else {
result.push(array1[i])
i++
j++
}
}
return result
}
console.log(mergeArray(arr1,arr2));

How to convert objects containing array into object of objects

My code:
function convert(arr, parent) {
var out = [];
for(var i in arr) {
if(arr[i].parent == parent) {
var children = convert(arr, arr[i].id)
if(children.length) {
arr[i].children = children
}
out.push(arr[i])
}
}
return out; //return Object.assign({}, out);tried this, but i lose parents childrens arrays
};
arras = [
{id: 1, name: "parent1", parent: null},
{id: 2, name: "children1", parent: 1},
{id: 3, name: "children2", parent: 1},
{id: 4, name: "parent2", parent: null},
{id: 5, name: "children3", parent: 4},
{id: 6, name: "children4", parent: 4}
]
console.log(convert(arras, null));
How final result should look
{
parent1: [
{name: "children1"},
{name: "children2"}
],
parent2: [
{name: "children3},
{name: "children4"}
]
}
What my output looks so far:
[
{id: 1, name: "parent1", parent: null}: [
{id: 2, name: "children1", parent: 1},
{id: 3, name: "children2", parent: 1},
],
{id: 4, name: "parent2", parent: null}: [
{id: 5, name: "children3", parent: 4},
{id: 6, name: "children4", parent: 4}
]
]
So firstly, what I have to do is convert main array to object, when I tend to do that, I lose both parent object arrays...Also need to change the way console displays objects, any help is appreciated.
You could build a tree with check if parent is a root node or not.
var data = [{ id: 1, name: "parent1", parent: null }, { id: 2, name: "children1", parent: 1 }, { id: 3, name: "children2", parent: 1 }, { id: 4, name: "parent2", parent: null }, { id: 5, name: "children3", parent: 4 }, { id: 6, name: "children4", parent: 4 }],
tree = function (data, root) {
var r = {},
o = {};
data.forEach(function (a) {
if (a.parent === root) {
r[a.name] = [];
o[a.id] = r[a.name];
} else {
o[a.parent] = o[a.parent] || [];
o[a.parent].push({ name: a.name });
}
});
return r;
}(data, null);
console.log(tree);
.as-console-wrapper { max-height: 100% !important; top: 0; }
Try this.
function convert(arr) {
var parents = {};
for (var i in arr) {
if (arr[i].parent === null) {
parents[arr[i].id] = arr[i].name
}
}
var out = {}
for (i in arr) {
if (arr[i].parent !== null) {
var parentName = parents[arr[i].parent];
if (out.hasOwnProperty(parentName)) {
out[parentName].push(arr[i].name)
} else {
out[parentName] = [arr[i].name]
}
}
}
return out;
};
arras = [{
id: 1,
name: "parent1",
parent: null
},
{
id: 2,
name: "children1",
parent: 1
},
{
id: 3,
name: "children2",
parent: 1
},
{
id: 4,
name: "parent2",
parent: null
},
{
id: 5,
name: "children3",
parent: 4
},
{
id: 6,
name: "children4",
parent: 4
}
]
//console.log(convert(arras, null));
alert(JSON.stringify(convert(arras)));
But notice for multilevel it doesn't work correctly. If your need it, your must save map for all possible parent list
arras.forEach(function(el){
if(el.parent){
el.parent=arras.find(e=>e.id==el.parent)||(console.error("no parent:"+el.parent),undefined);
}
});
//resolved parent/childs....
var newmodel = arras.reduce(function(obj,el){
if(el.parent){
//child
obj[el.parent.name]=obj[el.parent.name]||[];//create new parent if neccessary
obj[el.parent.name].push({name:el.name});
}else{
//parent
obj[el.name]=obj[el.name]||[];
}
return obj;
},{});
http://jsbin.com/renicijufi/edit?console
Another way:
var arrays = [
{id: 1, name: 'parent1', parent: null},
{id: 2, name: 'children1', parent: 1},
{id: 3, name: 'children2', parent: 1},
{id: 4, name: 'parent2', parent: null},
{id: 5, name: 'children3', parent: 4},
{id: 6, name: 'children4', parent: 4}
];
// First, reduce the input arrays to id based map
// This step help easy to select any element by id.
arrays = arrays.reduce(function (map, el) {
map[el.id] = el;
return map;
}, {});
var result = Object.values(arrays).reduce(function (result, el) {
if (!el.parent) {
result[el.name] = [];
} else {
result[arrays[el.parent].name].push(el.name);
}
return result;
}, {});
console.log(result);
I think this meets your requirement
Obj = new Object();
for( i in arras){
person = arras[i];
if(person.parent != null){
if(!Obj.hasOwnProperty(person.parent)){
// here instead of the index you can use Obj["parent"+person.parent] get the exact thing. If you are using that use tha in rest of the code
Obj[person.parent] = new Array();
}
Obj[person.parent].push(person);
}
else{
if(!Obj.hasOwnProperty(person.id)){
// Some parents might have kids not in the list. If you want to ignore, just remove from the else.
Obj[person.id] = new Array()
}
}
}
Edit :
Obj = new Object();
for( i in arras){
person = arras[i];
if(person.parent != null){
if(!Obj.hasOwnProperty(person.parent)){
// here instead of the index you can use Obj["parent"+person.parent] get the exact thing. If you are using that use tha in rest of the code
Obj[person.parent] = new Array();
}
Obj[person.parent].push({name : person.name});
}
else{
if(!Obj.hasOwnProperty(person.id)){
// Some parents might have kids not in the list. If you want to ignore, just remove from the else.
Obj[person.id] = new Array()
}
}
}
Hope this helps. :)

How to build a tree from a flat list in FP JS

I'm learning Functional Javascript and encounter into a problem.
I have this flat object:
const data = [
{id: 1, name: "Folder1", parentId: null},
{id: 2, name: "Folder2", parentId: null},
{id: 3, name: "Folder3", parentId: 1},
{id: 4, name: "Folder4", parentId: 2},
{id: 5, name: "Folder5", parentId: 3},
{id: 6, name: "Folder6", parentId: 3}
]
I desire to convert it to this hierarchical object, using only pure functions, no fors, ifs and other "imperative style statements".
Result should be:
[{
id: 1,
name: "Folder1",
parentId: null,
children = [{
id: 3,
name: "Folder3",
parentId: 1,
children = [{
id: 5,
name: "Folder5",
parentId: 3
},
{
id: 6,
name: "Folder6",
parentId: 3
}
]
}]
},
{
id: 2,
name: "Folder2",
parentId: null,
children = [{
id: 4,
name: "Folder4",
parentId: 2
}]
}
]
Any Ideas?
This is a proposal without if, but with Array#reduce and Map. It needs a sorted array.
var data = [{ id: 1, name: "Folder1", parentId: null }, { id: 2, name: "Folder2", parentId: null }, { id: 3, name: "Folder3", parentId: 1 }, { id: 4, name: "Folder4", parentId: 2 }, { id: 5, name: "Folder5", parentId: 3 }, { id: 6, name: "Folder6", parentId: 3 }],
tree = data
.reduce(
(m, a) => (
m
.get(a.parentId)
.push(Object.assign({}, a, { children: m.set(a.id, []).get(a.id) })),
m
),
new Map([[null, []]])
)
.get(null);
console.log(tree);
.as-console-wrapper { max-height: 100% !important; top: 0; }
Or the same as above using ES2015 destructuring assignment. It needs a sorted array and also depends on the input data having only id, name and parentId keys.
var data = [{ id: 1, name: "Folder1", parentId: null }, { id: 2, name: "Folder2", parentId: null }, { id: 3, name: "Folder3", parentId: 1 }, { id: 4, name: "Folder4", parentId: 2 }, { id: 5, name: "Folder5", parentId: 3 }, { id: 6, name: "Folder6", parentId: 3 }],
tree = data
.reduce(
(m, {id, name, parentId}) => (
m
.get(parentId)
.push({id, name, parentId, children: m.set(id, []).get(id) }),
m
),
new Map([[null, []]])
)
.get(null);
console.log(tree);
.as-console-wrapper { max-height: 100% !important; top: 0; }
Of course this should probably be written as a reusable function ...
var data = [{ id: 1, name: "Folder1", parentId: null }, { id: 2, name: "Folder2", parentId: null }, { id: 3, name: "Folder3", parentId: 1 }, { id: 4, name: "Folder4", parentId: 2 }, { id: 5, name: "Folder5", parentId: 3 }, { id: 6, name: "Folder6", parentId: 3 }];
// pure, reusable function
var buildTree = (data) =>
data.reduce(
(m, {id, name, parentId}) => (
m
.get(parentId)
.push({id, name, parentId, children: m.set(id, []).get(id) }),
m
),
new Map([[null, []]])
)
.get(null);
console.log(buildTree(data));
.as-console-wrapper { max-height: 100% !important; top: 0; }
Lastly, if the data is arriving in an unsorted order, we could handle sorting with a custom comparator
// unsorted data example
var data = [{ id: 6, name: "Folder6", parentId: 3 }, { id: 2, name: "Folder2", parentId: null }, { id: 3, name: "Folder3", parentId: 1 }, { id: 4, name: "Folder4", parentId: 2 }, { id: 5, name: "Folder5", parentId: 3 }, { id: 1, name: "Folder1", parentId: null }];
// immutable sort
var sort = (f,xs) => [...xs.sort(f)];
// custom tree comparator
var treeComparator = (x,y) =>
x.parentId - y.parentId || x.id - y.id;
// sort data, then reduce
var buildTree = (data) =>
sort(treeComparator, data).reduce(
(m, {id, name, parentId}) => (
m
.get(parentId)
.push({id, name, parentId, children: m.set(id, []).get(id) }),
m
),
new Map([[null, []]])
)
.get(null);
console.log(buildTree(data));
.as-console-wrapper { max-height: 100% !important; top: 0; }
You can do this with recursive function but you need to loop array with reduce and use if statements.
const arr = [
{id: 1, name: "Folder1", parentId: null},
{id: 2, name: "Folder2", parentId: null},
{id: 3, name: "Folder3", parentId: 1},
{id: 4, name: "Folder4", parentId: 2},
{id: 5, name: "Folder5", parentId: 3},
{id: 6, name: "Folder6", parentId: 3}
]
function buildTree(data, pId) {
return data.reduce(function(r, e) {
var e = Object.assign({}, e);
if (e.parentId == pId) {
var children = buildTree(data, e.id)
if (children.length) e.children = children
r.push(e)
}
return r;
}, [])
}
console.log(buildTree(arr, null))
const data = [
{id: 1, name: "Folder1", parentId: null},
{id: 2, name: "Folder2", parentId: null},
{id: 3, name: "Folder3", parentId: 1},
{id: 4, name: "Folder4", parentId: 2},
{id: 5, name: "Folder5", parentId: 3},
{id: 6, name: "Folder6", parentId: 3}
];
function trampoline ( f ) {
while ( f && f instanceof Function ) { f = f ( ); }
return f;
}
function buildTree ( data, copy, top = [] ) {
function recur ( data, copy, top ) {
copy = copy || data.concat ( [] );
let current = copy.shift ( );
current ? doWork ( ) : null;
function doWork ( ) {
top = top.concat ( ( ! current.parentId ? current : [] ) );
current.children = copy.filter ( x => { return current.id === x.parentId } );
}
return ( current ? recur.bind ( null, data, copy, top ) : top );
}
return trampoline ( recur.bind ( null, data, copy, top ) );
}
data.map ( x => { x [ 'children' ] = [ ]; return x; } );
console.log ( buildTree ( data ) );

Categories