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Javascript customize json data format [duplicate]

I have a complex json file that I have to handle with javascript to make it hierarchical, in order to later build a tree.
Every entry of the json has :
id : a unique id,
parentId : the id of the parent node (which is 0 if the node is a root of the tree)
level : the level of depth in the tree
The json data is already "ordered". I mean that an entry will have above itself a parent node or brother node, and under itself a child node or a brother node.
Input :
{
"People": [
{
"id": "12",
"parentId": "0",
"text": "Man",
"level": "1",
"children": null
},
{
"id": "6",
"parentId": "12",
"text": "Boy",
"level": "2",
"children": null
},
{
"id": "7",
"parentId": "12",
"text": "Other",
"level": "2",
"children": null
},
{
"id": "9",
"parentId": "0",
"text": "Woman",
"level": "1",
"children": null
},
{
"id": "11",
"parentId": "9",
"text": "Girl",
"level": "2",
"children": null
}
],
"Animals": [
{
"id": "5",
"parentId": "0",
"text": "Dog",
"level": "1",
"children": null
},
{
"id": "8",
"parentId": "5",
"text": "Puppy",
"level": "2",
"children": null
},
{
"id": "10",
"parentId": "13",
"text": "Cat",
"level": "1",
"children": null
},
{
"id": "14",
"parentId": "13",
"text": "Kitten",
"level": "2",
"children": null
},
]
}
Expected output :
{
"People": [
{
"id": "12",
"parentId": "0",
"text": "Man",
"level": "1",
"children": [
{
"id": "6",
"parentId": "12",
"text": "Boy",
"level": "2",
"children": null
},
{
"id": "7",
"parentId": "12",
"text": "Other",
"level": "2",
"children": null
}
]
},
{
"id": "9",
"parentId": "0",
"text": "Woman",
"level": "1",
"children":
{
"id": "11",
"parentId": "9",
"text": "Girl",
"level": "2",
"children": null
}
}
],
"Animals": [
{
"id": "5",
"parentId": "0",
"text": "Dog",
"level": "1",
"children":
{
"id": "8",
"parentId": "5",
"text": "Puppy",
"level": "2",
"children": null
}
},
{
"id": "10",
"parentId": "13",
"text": "Cat",
"level": "1",
"children":
{
"id": "14",
"parentId": "13",
"text": "Kitten",
"level": "2",
"children": null
}
}
]
}

There is an efficient solution if you use a map-lookup. If the parents always come before their children you can merge the two for-loops. It supports multiple roots. It gives an error on dangling branches, but can be modified to ignore them. It doesn't require a 3rd-party library. It's, as far as I can tell, the fastest solution.
function list_to_tree(list) {
var map = {}, node, roots = [], i;
for (i = 0; i < list.length; i += 1) {
map[list[i].id] = i; // initialize the map
list[i].children = []; // initialize the children
}
for (i = 0; i < list.length; i += 1) {
node = list[i];
if (node.parentId !== "0") {
// if you have dangling branches check that map[node.parentId] exists
list[map[node.parentId]].children.push(node);
} else {
roots.push(node);
}
}
return roots;
}
var entries = [{
"id": "12",
"parentId": "0",
"text": "Man",
"level": "1",
"children": null
},
{
"id": "6",
"parentId": "12",
"text": "Boy",
"level": "2",
"children": null
},
{
"id": "7",
"parentId": "12",
"text": "Other",
"level": "2",
"children": null
},
{
"id": "9",
"parentId": "0",
"text": "Woman",
"level": "1",
"children": null
},
{
"id": "11",
"parentId": "9",
"text": "Girl",
"level": "2",
"children": null
}
];
console.log(list_to_tree(entries));
If you're into complexity theory this solution is Θ(n log(n)). The recursive-filter solution is Θ(n^2) which can be a problem for large data sets.

( BONUS1 : NODES MAY or MAY NOT BE ORDERED )
( BONUS2 : NO 3RD PARTY LIBRARY NEEDED, PLAIN JS )
( BONUS3 : User "Elias Rabl" says this is the most performant solution, see his answer below )
Here it is:
const createDataTree = dataset => {
const hashTable = Object.create(null);
dataset.forEach(aData => hashTable[aData.ID] = {...aData, childNodes: []});
const dataTree = [];
dataset.forEach(aData => {
if(aData.parentID) hashTable[aData.parentID].childNodes.push(hashTable[aData.ID])
else dataTree.push(hashTable[aData.ID])
});
return dataTree;
};
Here is a test, it might help you to understand how the solution works :
it('creates a correct shape of dataTree', () => {
const dataSet = [{
"ID": 1,
"Phone": "(403) 125-2552",
"City": "Coevorden",
"Name": "Grady"
}, {
"ID": 2,
"parentID": 1,
"Phone": "(979) 486-1932",
"City": "Chełm",
"Name": "Scarlet"
}];
const expectedDataTree = [{
"ID": 1,
"Phone": "(403) 125-2552",
"City": "Coevorden",
"Name": "Grady",
childNodes: [{
"ID": 2,
"parentID": 1,
"Phone": "(979) 486-1932",
"City": "Chełm",
"Name": "Scarlet",
childNodes : []
}]
}];
expect(createDataTree(dataSet)).toEqual(expectedDataTree);
});

As mentioned by #Sander, #Halcyon`s answer assumes a pre-sorted array, the following does not. (It does however assume you have loaded underscore.js - though it could be written in vanilla javascript):
Code
// Example usage
var arr = [
{'id':1 ,'parentid' : 0},
{'id':2 ,'parentid' : 1},
{'id':3 ,'parentid' : 1},
{'id':4 ,'parentid' : 2},
{'id':5 ,'parentid' : 0},
{'id':6 ,'parentid' : 0},
{'id':7 ,'parentid' : 4}
];
unflatten = function( array, parent, tree ){
tree = typeof tree !== 'undefined' ? tree : [];
parent = typeof parent !== 'undefined' ? parent : { id: 0 };
var children = _.filter( array, function(child){ return child.parentid == parent.id; });
if( !_.isEmpty( children ) ){
if( parent.id == 0 ){
tree = children;
}else{
parent['children'] = children
}
_.each( children, function( child ){ unflatten( array, child ) } );
}
return tree;
}
tree = unflatten( arr );
document.body.innerHTML = "<pre>" + (JSON.stringify(tree, null, " "))
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>
Requirements
It assumes the properties 'id' and 'parentid' indicate ID and parent ID respectively. There must be elements with parent ID 0, otherwise you get an empty array back. Orphaned elements and their descendants are 'lost'
http://jsfiddle.net/LkkwH/1/

Use this ES6 approach. Works like charm
// Data Set
// One top level comment
const comments = [{
id: 1,
parent_id: null
}, {
id: 2,
parent_id: 1
}, {
id: 3,
parent_id: 1
}, {
id: 4,
parent_id: 2
}, {
id: 5,
parent_id: 4
}];
const nest = (items, id = null, link = 'parent_id') =>
items
.filter(item => item[link] === id)
.map(item => ({ ...item, children: nest(items, item.id) }));
console.log(
nest(comments)
)

Had the same problem, but I could not be certain that the data was sorted or not. I could not use a 3rd party library so this is just vanilla Js; Input data can be taken from #Stephen's example;
var arr = [
{'id':1 ,'parentid' : 0},
{'id':4 ,'parentid' : 2},
{'id':3 ,'parentid' : 1},
{'id':5 ,'parentid' : 0},
{'id':6 ,'parentid' : 0},
{'id':2 ,'parentid' : 1},
{'id':7 ,'parentid' : 4},
{'id':8 ,'parentid' : 1}
];
function unflatten(arr) {
var tree = [],
mappedArr = {},
arrElem,
mappedElem;
// First map the nodes of the array to an object -> create a hash table.
for(var i = 0, len = arr.length; i < len; i++) {
arrElem = arr[i];
mappedArr[arrElem.id] = arrElem;
mappedArr[arrElem.id]['children'] = [];
}
for (var id in mappedArr) {
if (mappedArr.hasOwnProperty(id)) {
mappedElem = mappedArr[id];
// If the element is not at the root level, add it to its parent array of children.
if (mappedElem.parentid) {
mappedArr[mappedElem['parentid']]['children'].push(mappedElem);
}
// If the element is at the root level, add it to first level elements array.
else {
tree.push(mappedElem);
}
}
}
return tree;
}
var tree = unflatten(arr);
document.body.innerHTML = "<pre>" + (JSON.stringify(tree, null, " "))
JS Fiddle
Flat Array to Tree

a more simple function list-to-tree-lite
npm install list-to-tree-lite
listToTree(list)
source:
function listToTree(data, options) {
options = options || {};
var ID_KEY = options.idKey || 'id';
var PARENT_KEY = options.parentKey || 'parent';
var CHILDREN_KEY = options.childrenKey || 'children';
var tree = [],
childrenOf = {};
var item, id, parentId;
for (var i = 0, length = data.length; i < length; i++) {
item = data[i];
id = item[ID_KEY];
parentId = item[PARENT_KEY] || 0;
// every item may have children
childrenOf[id] = childrenOf[id] || [];
// init its children
item[CHILDREN_KEY] = childrenOf[id];
if (parentId != 0) {
// init its parent's children object
childrenOf[parentId] = childrenOf[parentId] || [];
// push it into its parent's children object
childrenOf[parentId].push(item);
} else {
tree.push(item);
}
};
return tree;
}
jsfiddle

You can handle this question with just two line coding:
_(flatArray).forEach(f=>
{f.nodes=_(flatArray).filter(g=>g.parentId==f.id).value();});
var resultArray=_(flatArray).filter(f=>f.parentId==null).value();
Test Online (see the browser console for created tree)
Requirements:
1- Install lodash 4 (a Javascript library for manipulating objects and collections with performant methods => like the Linq in c#) Lodash
2- A flatArray like below:
var flatArray=
[{
id:1,parentId:null,text:"parent1",nodes:[]
}
,{
id:2,parentId:null,text:"parent2",nodes:[]
}
,
{
id:3,parentId:1,text:"childId3Parent1",nodes:[]
}
,
{
id:4,parentId:1,text:"childId4Parent1",nodes:[]
}
,
{
id:5,parentId:2,text:"childId5Parent2",nodes:[]
}
,
{
id:6,parentId:2,text:"childId6Parent2",nodes:[]
}
,
{
id:7,parentId:3,text:"childId7Parent3",nodes:[]
}
,
{
id:8,parentId:5,text:"childId8Parent5",nodes:[]
}];
Thank Mr. Bakhshabadi
Good luck

It may be useful package list-to-tree
Install:
bower install list-to-tree --save
or
npm install list-to-tree --save
For example, have list:
var list = [
{
id: 1,
parent: 0
}, {
id: 2,
parent: 1
}, {
id: 3,
parent: 1
}, {
id: 4,
parent: 2
}, {
id: 5,
parent: 2
}, {
id: 6,
parent: 0
}, {
id: 7,
parent: 0
}, {
id: 8,
parent: 7
}, {
id: 9,
parent: 8
}, {
id: 10,
parent: 0
}
];
Use package list-to-tree:
var ltt = new LTT(list, {
key_id: 'id',
key_parent: 'parent'
});
var tree = ltt.GetTree();
Result:
[{
"id": 1,
"parent": 0,
"child": [
{
"id": 2,
"parent": 1,
"child": [
{
"id": 4,
"parent": 2
}, {
"id": 5, "parent": 2
}
]
},
{
"id": 3,
"parent": 1
}
]
}, {
"id": 6,
"parent": 0
}, {
"id": 7,
"parent": 0,
"child": [
{
"id": 8,
"parent": 7,
"child": [
{
"id": 9,
"parent": 8
}
]
}
]
}, {
"id": 10,
"parent": 0
}];

I've written a test script to evaluate the performance of the two most general solutions (meaning that the input does not have to be sorted beforehand and that the code does not depend on third party libraries), proposed by users shekhardtu (see answer) and FurkanO (see answer).
http://playcode.io/316025?tabs=console&script.js&output
FurkanO's solution seems to be the fastest.
/*
** performance test for https://stackoverflow.com/questions/18017869/build-tree-array-from-flat-array-in-javascript
*/
// Data Set (e.g. nested comments)
var comments = [{
id: 1,
parent_id: null
}, {
id: 2,
parent_id: 1
}, {
id: 3,
parent_id: 4
}, {
id: 4,
parent_id: null
}, {
id: 5,
parent_id: 4
}];
// add some random entries
let maxParentId = 10000;
for (let i=6; i<=maxParentId; i++)
{
let randVal = Math.floor((Math.random() * maxParentId) + 1);
comments.push({
id: i,
parent_id: (randVal % 200 === 0 ? null : randVal)
});
}
// solution from user "shekhardtu" (https://stackoverflow.com/a/55241491/5135171)
const nest = (items, id = null, link = 'parent_id') =>
items
.filter(item => item[link] === id)
.map(item => ({ ...item, children: nest(items, item.id) }));
;
// solution from user "FurkanO" (https://stackoverflow.com/a/40732240/5135171)
const createDataTree = dataset => {
let hashTable = Object.create(null)
dataset.forEach( aData => hashTable[aData.id] = { ...aData, children : [] } )
let dataTree = []
dataset.forEach( aData => {
if( aData.parent_id ) hashTable[aData.parent_id].children.push(hashTable[aData.id])
else dataTree.push(hashTable[aData.id])
} )
return dataTree
};
/*
** lets evaluate the timing for both methods
*/
let t0 = performance.now();
let createDataTreeResult = createDataTree(comments);
let t1 = performance.now();
console.log("Call to createDataTree took " + Math.floor(t1 - t0) + " milliseconds.");
t0 = performance.now();
let nestResult = nest(comments);
t1 = performance.now();
console.log("Call to nest took " + Math.floor(t1 - t0) + " milliseconds.");
//console.log(nestResult);
//console.log(createDataTreeResult);
// bad, but simple way of comparing object equality
console.log(JSON.stringify(nestResult)===JSON.stringify(createDataTreeResult));

After many tries I came up with this:
const arrayToTree = (arr, parent = 0) => arr .filter(item => item.parent === parent).map(child => ({ ...child, children: arrayToTree(arr, child.index) }));
const entries = [
{
index: 1,
parent: 0
},
{
index: 2,
parent: 1
},
{
index: 3,
parent: 2
},
{
index: 4,
parent: 2
},
{
index: 5,
parent: 4
},
{
index: 6,
parent: 5
},
{
index: 7,
parent: 6
},
{
index: 8,
parent: 7
},
{
index: 9,
parent: 8
},
{
index: 10,
parent: 9
},
{
index: 11,
parent: 7
},
{
index: 13,
parent: 11
},
{
index: 12,
parent: 0
}
];
const arrayToTree = (arr, parent = 0) => arr .filter(item => item.parent === parent) .map(child => ({ ...child, children: arrayToTree(arr, child.index) })); console.log(arrayToTree(entries));

UPDATE 2022
This is a proposal for unordered items. This function works with a single loop and with a hash table and collects all items with their id. If a root node is found, then the object is added to the result array.
const
getTree = (data, root) => {
const t = {};
data.forEach(o => ((t[o.parentId] ??= {}).children ??= []).push(Object.assign(t[o.id] ??= {}, o)));
return t[root].children;
},
data = { People: [{ id: "12", parentId: "0", text: "Man", level: "1", children: null }, { id: "6", parentId: "12", text: "Boy", level: "2", children: null }, { id: "7", parentId: "12", text: "Other", level: "2", children: null }, { id: "9", parentId: "0", text: "Woman", level: "1", children: null }, { id: "11", parentId: "9", text: "Girl", level: "2", children: null }], Animals: [{ id: "5", parentId: "0", text: "Dog", level: "1", children: null }, { id: "8", parentId: "5", text: "Puppy", level: "2", children: null }, { id: "10", parentId: "13", text: "Cat", level: "1", children: null }, { id: "14", parentId: "13", text: "Kitten", level: "2", children: null }] },
result = Object.fromEntries(Object
.entries(data)
.map(([k, v]) => [k, getTree(v, '0')])
);
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

I like #WilliamLeung's pure JavaScript solution, but sometimes you need to make changes in existing array to keep a reference to object.
function listToTree(data, options) {
options = options || {};
var ID_KEY = options.idKey || 'id';
var PARENT_KEY = options.parentKey || 'parent';
var CHILDREN_KEY = options.childrenKey || 'children';
var item, id, parentId;
var map = {};
for(var i = 0; i < data.length; i++ ) { // make cache
if(data[i][ID_KEY]){
map[data[i][ID_KEY]] = data[i];
data[i][CHILDREN_KEY] = [];
}
}
for (var i = 0; i < data.length; i++) {
if(data[i][PARENT_KEY]) { // is a child
if(map[data[i][PARENT_KEY]]) // for dirty data
{
map[data[i][PARENT_KEY]][CHILDREN_KEY].push(data[i]); // add child to parent
data.splice( i, 1 ); // remove from root
i--; // iterator correction
} else {
data[i][PARENT_KEY] = 0; // clean dirty data
}
}
};
return data;
}
Exapmle:
https://jsfiddle.net/kqw1qsf0/17/

Convert nodes Array to Tree
ES6 function to convert an Array of nodes (related by parent ID) - to a Tree structure:
/**
* Convert nodes list related by parent ID - to tree.
* #syntax getTree(nodesArray [, rootID [, propertyName]])
*
* #param {Array} arr Array of nodes
* #param {integer} id Defaults to 0
* #param {string} p Property name. Defaults to "parent_id"
* #returns {Object} Nodes tree
*/
const getTree = (arr, p = "parent_id") => arr.reduce((o, n) => {
if (!o[n.id]) o[n.id] = {};
if (!o[n[p]]) o[n[p]] = {};
if (!o[n[p]].nodes) o[n[p]].nodes= [];
if (o[n.id].nodes) n.nodes= o[n.id].nodes;
o[n[p]].nodes.push(n);
o[n.id] = n;
return o;
}, {});
Generate HTML List from nodes Tree
Having our Tree in place, here's a recursive function to build the UL > LI Elements:
/**
* Convert Tree structure to UL>LI and append to Element
* #syntax getTree(treeArray [, TargetElement [, onLICreatedCallback ]])
*
* #param {Array} tree Tree array of nodes
* #param {Element} el HTMLElement to insert into
* #param {function} cb Callback function called on every LI creation
*/
const treeToHTML = (tree, el, cb) => el.append(tree.reduce((ul, n) => {
const li = document.createElement('li');
if (cb) cb.call(li, n);
if (n.nodes?.length) treeToHTML(n.nodes, li, cb);
ul.append(li);
return ul;
}, document.createElement('ul')));
Demo time
Here's an example having a linear Array of nodes and using both the above functions:
const getTree = (arr, p = "parent_id") => arr.reduce((o, n) => {
if (!o[n.id]) o[n.id] = {};
if (!o[n[p]]) o[n[p]] = {};
if (!o[n[p]].nodes) o[n[p]].nodes = [];
if (o[n.id].nodes) n.nodes = o[n.id].nodes;
o[n[p]].nodes.push(n);
o[n.id] = n;
return o;
}, {});
const treeToHTML = (tree, el, cb) => el.append(tree.reduce((ul, n) => {
const li = document.createElement('li');
if (cb) cb.call(li, n);
if (n.nodes?.length) treeToHTML(n.nodes, li, cb);
ul.append(li);
return ul;
}, document.createElement('ul')));
// DEMO TIME:
const nodesList = [
{id: 10, parent_id: 4, text: "Item 10"}, // PS: Order does not matters
{id: 1, parent_id: 0, text: "Item 1"},
{id: 4, parent_id: 0, text: "Item 4"},
{id: 3, parent_id: 5, text: "Item 3"},
{id: 5, parent_id: 4, text: "Item 5"},
{id: 2, parent_id: 1, text: "Item 2"},
];
const myTree = getTree(nodesList)[0].nodes; // Get nodes of Root (0)
treeToHTML(myTree, document.querySelector("#tree"), function(node) {
this.textContent = `(${node.parent_id} ${node.id}) ${node.text}`;
this._node = node;
this.addEventListener('click', clickHandler);
});
function clickHandler(ev) {
if (ev.target !== this) return;
console.clear();
console.log(this._node.id);
};
<div id="tree"></div>

Array elements can be in a chaotic order
let array = [
{ id: 1, data: 'something', parent_id: null, children: [] },
{ id: 2, data: 'something', parent_id: 1, children: [] },
{ id: 5, data: 'something', parent_id: 4, children: [] },
{ id: 4, data: 'something', parent_id: 3, children: [] },
{ id: 3, data: 'something', parent_id: null, children: [] },
{ id: 6, data: 'something', parent_id: null, children: [] }
]
function buildTree(array) {
let tree = []
for (let i = 0; i < array.length; i++) {
if (array[i].parent_id) {
let parent = array.filter(elem => elem.id === array[i].parent_id).pop()
parent.children.push(array[i])
} else {
tree.push(array[i])
}
}
return tree
}
const tree = buildTree(array)
console.log(tree);
.as-console-wrapper { min-height: 100% }

var data = [{"country":"india","gender":"male","type":"lower","class":"X"},
{"country":"china","gender":"female","type":"upper"},
{"country":"india","gender":"female","type":"lower"},
{"country":"india","gender":"female","type":"upper"}];
var seq = ["country","type","gender","class"];
var treeData = createHieArr(data,seq);
console.log(treeData)
function createHieArr(data,seq){
var hieObj = createHieobj(data,seq,0),
hieArr = convertToHieArr(hieObj,"Top Level");
return [{"name": "Top Level", "parent": "null",
"children" : hieArr}]
function convertToHieArr(eachObj,parent){
var arr = [];
for(var i in eachObj){
arr.push({"name":i,"parent":parent,"children":convertToHieArr(eachObj[i],i)})
}
return arr;
}
function createHieobj(data,seq,ind){
var s = seq[ind];
if(s == undefined){
return [];
}
var childObj = {};
for(var ele of data){
if(ele[s] != undefined){
if(childObj[ele[s]] == undefined){
childObj[ele[s]] = [];
}
childObj[ele[s]].push(ele);
}
}
ind = ind+1;
for(var ch in childObj){
childObj[ch] = createHieobj(childObj[ch],seq,ind)
}
return childObj;
}
}

this is what i used in a react project
// ListToTree.js
import _filter from 'lodash/filter';
import _map from 'lodash/map';
export default (arr, parentIdKey) => _map(_filter(arr, ar => !ar[parentIdKey]), ar => ({
...ar,
children: _filter(arr, { [parentIdKey]: ar.id }),
}));
usage:
// somewhere.js
import ListToTree from '../Transforms/ListToTree';
const arr = [
{
"id":"Bci6XhCLZKPXZMUztm1R",
"name":"Sith"
},
{
"id":"C3D71CMmASiR6FfDPlEy",
"name":"Luke",
"parentCategoryId":"ltatOlEkHdVPf49ACCMc"
},
{
"id":"aS8Ag1BQqxkO6iWBFnsf",
"name":"Obi Wan",
"parentCategoryId":"ltatOlEkHdVPf49ACCMc"
},
{
"id":"ltatOlEkHdVPf49ACCMc",
"name":"Jedi"
},
{
"id":"pw3CNdNhnbuxhPar6nOP",
"name":"Palpatine",
"parentCategoryId":"Bci6XhCLZKPXZMUztm1R"
}
];
const response = ListToTree(arr, 'parentCategoryId');
output:
[
{
"id":"Bci6XhCLZKPXZMUztm1R",
"name":"Sith",
"children":[
{
"id":"pw3CNdNhnbuxhPar6nOP",
"name":"Palpatine",
"parentCategoryId":"Bci6XhCLZKPXZMUztm1R"
}
]
},
{
"id":"ltatOlEkHdVPf49ACCMc",
"name":"Jedi",
"children":[
{
"id":"C3D71CMmASiR6FfDPlEy",
"name":"Luke",
"parentCategoryId":"ltatOlEkHdVPf49ACCMc"
},
{
"id":"aS8Ag1BQqxkO6iWBFnsf",
"name":"Obi Wan",
"parentCategoryId":"ltatOlEkHdVPf49ACCMc"
}
]
}
]```

I had similar issue couple days ago when have to display folder tree from flat array. I didn't see any solution in TypeScript here so I hope it will be helpful.
In my cases main parent were only one, also rawData array don't have to be sorted. Solutions base on prepare temp object like
{parentId: [child1, child2, ...] }
example raw data
const flatData: any[] = Folder.ofCollection([
{id: '1', title: 'some title' },
{id: '2', title: 'some title', parentId: 1 },
{id: '3', title: 'some title', parentId: 7 },
{id: '4', title: 'some title', parentId: 1 },
{id: '5', title: 'some title', parentId: 2 },
{id: '6', title: 'some title', parentId: 5 },
{id: '7', title: 'some title', parentId: 5 },
]);
def of Folder
export default class Folder {
public static of(data: any): Folder {
return new Folder(data);
}
public static ofCollection(objects: any[] = []): Folder[] {
return objects.map((obj) => new Folder(obj));
}
public id: string;
public parentId: string | null;
public title: string;
public children: Folder[];
constructor(data: any = {}) {
this.id = data.id;
this.parentId = data.parentId || null;
this.title = data.title;
this.children = data.children || [];
}
}
SOLUTION: Function that returns tree structure for flat argument
public getTree(flatData: any[]): Folder[] {
const addChildren = (item: Folder) => {
item.children = tempChild[item.id] || [];
if (item.children.length) {
item.children.forEach((child: Folder) => {
addChildren(child);
});
}
};
const tempChild: any = {};
flatData.forEach((item: Folder) => {
const parentId = item.parentId || 0;
Array.isArray(tempChild[parentId]) ? tempChild[parentId].push(item) : (tempChild[parentId] = [item]);
});
const tree: Folder[] = tempChild[0];
tree.forEach((base: Folder) => {
addChildren(base);
});
return tree;
}

I wrote an ES6 version based on #Halcyon answer
const array = [
{
id: '12',
parentId: '0',
text: 'one-1'
},
{
id: '6',
parentId: '12',
text: 'one-1-6'
},
{
id: '7',
parentId: '12',
text: 'one-1-7'
},
{
id: '9',
parentId: '0',
text: 'one-2'
},
{
id: '11',
parentId: '9',
text: 'one-2-11'
}
];
// Prevent changes to the original data
const arrayCopy = array.map(item => ({ ...item }));
const listToTree = list => {
const map = {};
const roots = [];
list.forEach((v, i) => {
map[v.id] = i;
list[i].children = [];
});
list.forEach(v => (v.parentId !== '0' ? list[map[v.parentId]].children.push(v) : roots.push(v)));
return roots;
};
console.log(listToTree(arrayCopy));
The principle of this algorithm is to use "map" to establish an index relationship. It is easy to find "item" in the list by "parentId", and add "children" to each "item", because "list" is a reference relationship, so "roots" will Build relationships with the entire tree.

Based on #FurkanO's answer, I created another version that does not mutate the origial data (like #Dac0d3r requested). I really liked #shekhardtu's answer, but realized it had to filter through the data many times. I thought a solution could be to use FurkanO's answer by copying the data first. I tried my version in jsperf, and the results where unfortunately (very) bleak... It seems like the accepted answer is really a good one! My version is quite configurable and failsafe though, so I share it with you guys anyway; here is my contribution:
function unflat(data, options = {}) {
const { id, parentId, childrenKey } = {
id: "id",
parentId: "parentId",
childrenKey: "children",
...options
};
const copiesById = data.reduce(
(copies, datum) => ((copies[datum[id]] = datum) && copies),
{}
);
return Object.values(copiesById).reduce(
(root, datum) => {
if ( datum[parentId] && copiesById[datum[parentId]] ) {
copiesById[datum[parentId]][childrenKey] = [ ...copiesById[datum[parentId]][childrenKey], datum ];
} else {
root = [ ...root, datum ];
}
return root
}, []
);
}
const data = [
{
"account": "10",
"name": "Konto 10",
"parentAccount": null
},{
"account": "1010",
"name": "Konto 1010",
"parentAccount": "10"
},{
"account": "10101",
"name": "Konto 10101",
"parentAccount": "1010"
},{
"account": "10102",
"name": "Konto 10102",
"parentAccount": "1010"
},{
"account": "10103",
"name": "Konto 10103",
"parentAccount": "1010"
},{
"account": "20",
"name": "Konto 20",
"parentAccount": null
},{
"account": "2020",
"name": "Konto 2020",
"parentAccount": "20"
},{
"account": "20201",
"name": "Konto 20201",
"parentAccount": "2020"
},{
"account": "20202",
"name": "Konto 20202",
"parentAccount": "2020"
}
];
const options = {
id: "account",
parentId: "parentAccount",
childrenKey: "children"
};
console.log(
"Hierarchical tree",
unflat(data, options)
);
With the options parameter, it is possible to configure what property to use as id or parent id. It is also possible to configure the name of the children property, if someone wants "childNodes": [] or something.
OP could simply use default options:
input.People = unflat(input.People);
If the parent id is falsy (null, undefined or other falsy values) or the parent object does not exist, we consider the object to be a root node.

My solution:
Allows bi-directional mapping (root to leaves and leaves to root)
Returns all nodes, roots, and leaves
One data pass and very fast performance
Vanilla Javascript
/**
*
* #param data items array
* #param idKey item's id key (e.g., item.id)
* #param parentIdKey item's key that points to parent (e.g., item.parentId)
* #param noParentValue item's parent value when root (e.g., item.parentId === noParentValue => item is root)
* #param bidirectional should parent reference be added
*/
function flatToTree(data, idKey, parentIdKey, noParentValue = null, bidirectional = true) {
const nodes = {}, roots = {}, leaves = {};
// iterate over all data items
for (const i of data) {
// add item as a node and possibly as a leaf
if (nodes[i[idKey]]) { // already seen this item when child was found first
// add all of the item's data and found children
nodes[i[idKey]] = Object.assign(nodes[i[idKey]], i);
} else { // never seen this item
// add to the nodes map
nodes[i[idKey]] = Object.assign({ $children: []}, i);
// assume it's a leaf for now
leaves[i[idKey]] = nodes[i[idKey]];
}
// put the item as a child in parent item and possibly as a root
if (i[parentIdKey] !== noParentValue) { // item has a parent
if (nodes[i[parentIdKey]]) { // parent already exist as a node
// add as a child
(nodes[i[parentIdKey]].$children || []).push( nodes[i[idKey]] );
} else { // parent wasn't seen yet
// add a "dummy" parent to the nodes map and put the item as its child
nodes[i[parentIdKey]] = { $children: [ nodes[i[idKey]] ] };
}
if (bidirectional) {
// link to the parent
nodes[i[idKey]].$parent = nodes[i[parentIdKey]];
}
// item is definitely not a leaf
delete leaves[i[parentIdKey]];
} else { // this is a root item
roots[i[idKey]] = nodes[i[idKey]];
}
}
return {roots, nodes, leaves};
}
Usage example:
const data = [{id: 2, parentId: 0}, {id: 1, parentId: 2} /*, ... */];
const { nodes, roots, leaves } = flatToTree(data, 'id', 'parentId', 0);

ES6 Map version :
getTreeData = (items) => {
if (items && items.length > 0) {
const data = [];
const map = {};
items.map((item) => {
const id = item.id; // custom id selector !!!
if (!map.hasOwnProperty(id)) {
// in case of duplicates
map[id] = {
...item,
children: [],
};
}
});
for (const id in map) {
if (map.hasOwnProperty(id)) {
let mappedElem = [];
mappedElem = map[id];
/// parentId : use custom id selector for parent
if (
mappedElem.parentId &&
typeof map[mappedElem.parentId] !== "undefined"
) {
map[mappedElem.parentId].children.push(mappedElem);
} else {
data.push(mappedElem);
}
}
}
return data;
}
return [];
};
/// use like this :
const treeData = getTreeData(flatList);

Incase anyone needs it for multiple parent. Refer id 2 which has multiple parents
const dataSet = [{
"ID": 1,
"Phone": "(403) 125-2552",
"City": "Coevorden",
"Name": "Grady"
},
{"ID": 2,
"Phone": "(403) 125-2552",
"City": "Coevorden",
"Name": "Grady"
},
{
"ID": 3,
"parentID": [1,2],
"Phone": "(979) 486-1932",
"City": "Chełm",
"Name": "Scarlet"
}];
const expectedDataTree = [
{
"ID":1,
"Phone":"(403) 125-2552",
"City":"Coevorden",
"Name":"Grady",
"childNodes":[{
"ID":2,
"parentID":[1,3],
"Phone":"(979) 486-1932",
"City":"Chełm",
"Name":"Scarlet",
"childNodes":[]
}]
},
{
"ID":3,
"parentID":[],
"Phone":"(403) 125-2552",
"City":"Coevorden",
"Name":"Grady",
"childNodes":[
{
"ID":2,
"parentID":[1,3],
"Phone":"(979) 486-1932",
"City":"Chełm",
"Name":"Scarlet",
"childNodes":[]
}
]
}
];
const createDataTree = dataset => {
const hashTable = Object.create(null);
dataset.forEach(aData => hashTable[aData.ID] = {...aData, childNodes: []});
const dataTree = [];
dataset.forEach(Datae => {
if (Datae.parentID && Datae.parentID.length > 0) {
Datae.parentID.forEach( aData => {
hashTable[aData].childNodes.push(hashTable[Datae.ID])
});
}
else{
dataTree.push(hashTable[Datae.ID])
}
});
return dataTree;
};
window.alert(JSON.stringify(createDataTree(dataSet)));

I used #FurkanO answer and made a generic function that can be used with any object type, I also wrote this function in TypeScript which i love it more because of auto completions.
Implementation:
1. Javascript:
export const flatListToTree = (flatList, idPath, parentIdPath, childListPath, isParent) => {
const rootParents = [];
const map = {};
for (const item of flatList) {
if (!item[childListPath]) item[childListPath] = [];
map[item[idPath]] = item;
}
for (const item of flatList) {
const parentId = item[parentIdPath];
if (isParent(item)) {
rootParents.push(item);
} else {
const parentItem = map[parentId];
parentItem[childListPath].push(item);
}
}
return rootParents;
};
2. TypeScript: I've assumed the "T" type has a property for children List, you can change 'childListPath' to be a string instead of "keyof T" if you have different use case.
export const flatListToTree = <T>(
flatList: T[],
idPath: keyof T,
parentIdPath: keyof T,
childListPath: keyof T,
isParent: (t: T) => boolean,
) => {
const rootParents: T[] = [];
const map: any = {};
for (const item of flatList) {
if (!(item as any)[childListPath]) (item as any)[childListPath] = [];
map[item[idPath]] = item;
}
for (const item of flatList) {
const parentId = item[parentIdPath];
if (isParent(item)) {
rootParents.push(item);
} else {
const parentItem = map[parentId];
parentItem[childListPath].push(item);
}
}
return rootParents;
};
How to use:
const nodes = [
{ id: 2, pid: undefined, children: [] },
{ id: 3, pid: 2 },
{ id: 4, pid: 2 },
{ id: 5, pid: 4 },
{ id: 6, pid: 5 },
{ id: 7, pid: undefined },
{ id: 8, pid: 7 },
];
const result = flatListToTree(nodes, "id", "pid", "children", node => node.pid === undefined);

Here's a simple helper function that I created modeled after the above answers, tailored to a Babel environment:
import { isEmpty } from 'lodash'
export default function unflattenEntities(entities, parent = {id: null}, tree = []) {
let children = entities.filter( entity => entity.parent_id == parent.id)
if (!isEmpty( children )) {
if ( parent.id == null ) {
tree = children
} else {
parent['children'] = children
}
children.map( child => unflattenEntities( entities, child ) )
}
return tree
}

also do it with lodashjs(v4.x)
function buildTree(arr){
var a=_.keyBy(arr, 'id')
return _
.chain(arr)
.groupBy('parentId')
.forEach(function(v,k){
k!='0' && (a[k].children=(a[k].children||[]).concat(v));
})
.result('0')
.value();
}

Here is a modified version of Steven Harris' that is plain ES5 and returns an object keyed on the id rather than returning an array of nodes at both the top level and for the children.
unflattenToObject = function(array, parent) {
var tree = {};
parent = typeof parent !== 'undefined' ? parent : {id: 0};
var childrenArray = array.filter(function(child) {
return child.parentid == parent.id;
});
if (childrenArray.length > 0) {
var childrenObject = {};
// Transform children into a hash/object keyed on token
childrenArray.forEach(function(child) {
childrenObject[child.id] = child;
});
if (parent.id == 0) {
tree = childrenObject;
} else {
parent['children'] = childrenObject;
}
childrenArray.forEach(function(child) {
unflattenToObject(array, child);
})
}
return tree;
};
var arr = [
{'id':1 ,'parentid': 0},
{'id':2 ,'parentid': 1},
{'id':3 ,'parentid': 1},
{'id':4 ,'parentid': 2},
{'id':5 ,'parentid': 0},
{'id':6 ,'parentid': 0},
{'id':7 ,'parentid': 4}
];
tree = unflattenToObject(arr);

This is a modified version of the above that works with multiple root items, I use GUIDs for my ids and parentIds so in the UI that creates them I hard code root items to something like 0000000-00000-00000-TREE-ROOT-ITEM
var tree = unflatten(records, "TREE-ROOT-ITEM");
function unflatten(records, rootCategoryId, parent, tree){
if(!_.isArray(tree)){
tree = [];
_.each(records, function(rec){
if(rec.parentId.indexOf(rootCategoryId)>=0){ // change this line to compare a root id
//if(rec.parentId == 0 || rec.parentId == null){ // example for 0 or null
var tmp = angular.copy(rec);
tmp.children = _.filter(records, function(r){
return r.parentId == tmp.id;
});
tree.push(tmp);
//console.log(tree);
_.each(tmp.children, function(child){
return unflatten(records, rootCategoryId, child, tree);
});
}
});
}
else{
if(parent){
parent.children = _.filter(records, function(r){
return r.parentId == parent.id;
});
_.each(parent.children, function(child){
return unflatten(records, rootCategoryId, child, tree);
});
}
}
return tree;
}

Copied from the Internet
http://jsfiddle.net/stywell/k9x2a3g6/
function list2tree(data, opt) {
opt = opt || {};
var KEY_ID = opt.key_id || 'ID';
var KEY_PARENT = opt.key_parent || 'FatherID';
var KEY_CHILD = opt.key_child || 'children';
var EMPTY_CHILDREN = opt.empty_children;
var ROOT_ID = opt.root_id || 0;
var MAP = opt.map || {};
function getNode(id) {
var node = []
for (var i = 0; i < data.length; i++) {
if (data[i][KEY_PARENT] == id) {
for (var k in MAP) {
data[i][k] = data[i][MAP[k]];
}
if (getNode(data[i][KEY_ID]) !== undefined) {
data[i][KEY_CHILD] = getNode(data[i][KEY_ID]);
} else {
if (EMPTY_CHILDREN === null) {
data[i][KEY_CHILD] = null;
} else if (JSON.stringify(EMPTY_CHILDREN) === '[]') {
data[i][KEY_CHILD] = [];
}
}
node.push(data[i]);
}
}
if (node.length == 0) {
return;
} else {
return node;
}
}
return getNode(ROOT_ID)
}
var opt = {
"key_id": "ID", //节点的ID
"key_parent": "FatherID", //节点的父级ID
"key_child": "children", //子节点的名称
"empty_children": [], //子节点为空时,填充的值 //这个参数为空时,没有子元素的元素不带key_child属性;还可以为null或者[],同理
"root_id": 0, //根节点的父级ID
"map": { //在节点内映射一些值 //对象的键是节点的新属性; 对象的值是节点的老属性,会赋值给新属性
"value": "ID",
"label": "TypeName",
}
};

You can use npm package array-to-tree https://github.com/alferov/array-to-tree.
It's convert a plain array of nodes (with pointers to parent nodes) to a nested data structure.
Solves a problem with conversion of retrieved from a database sets of data to a nested data structure (i.e. navigation tree).
Usage:
var arrayToTree = require('array-to-tree');
var dataOne = [
{
id: 1,
name: 'Portfolio',
parent_id: undefined
},
{
id: 2,
name: 'Web Development',
parent_id: 1
},
{
id: 3,
name: 'Recent Works',
parent_id: 2
},
{
id: 4,
name: 'About Me',
parent_id: undefined
}
];
arrayToTree(dataOne);
/*
* Output:
*
* Portfolio
* Web Development
* Recent Works
* About Me
*/

You can use this "treeify" package from Github here or NPM.
Installation:
$ npm install --save-dev treeify-js

Group array of objects with a specific key value pushed first

Given the following Array of Objects:
[
{
"teamFK": 8650,
"code": "yellow_cards",
"typeId": 554,
"value": "5",
"side": "home"
},
{
"teamFK": 8650,
"code": "goals",
"typeId": 554,
"value": "1",
"side": "home"
},
{
"teamFK": 8990,
"code": "yellow_cards",
"typeId": 555,
"value": "2",
"side": "away"
},
{
"teamFK": 8990,
"code": "goals",
"typeId": 555,
"value": "0",
"side": "away"
}
]
I would like to group this data by code and get this result:
{
"stats": [
{
"name": "yellow_cards",
"stats": ["5","2"]
},
{
"name": "goals",
"stats": ["2","0"]
}
]
}
What I've done is the following which works but I want to make sure that the alway the stat with "side":"home" always pushed first into the array "stats": []:
const groupedStats = Object.entries(
query.reduce((acc, { typeId, value, code, side }) => {
if (!acc[code]) {
acc[code] = [];
}
acc[code].push(value);
return acc;
}, {}),
).map(([name, stats]) => ({ name, stats }));

My approach is sort it first by side using Array.sort() and then looping through the objects and adding it to stats
i created a const match to find if there is a match already so i dont have to add the name and value again basically if its not a match i'll add it to the stats array and if its a match then i'll just update the current index
const objs = [
{
teamFK: 8650,
code: "yellow_cards",
typeId: 554,
value: "5",
side: "home",
},
{
teamFK: 8650,
code: "goals",
typeId: 554,
value: "1",
side: "away",
},
{
teamFK: 8990,
code: "yellow_cards",
typeId: 555,
value: "2",
side: "away",
},
{
teamFK: 8990,
code: "goals",
typeId: 555,
value: "0",
side: "home",
},
];
let stats = [];
const transformedObj = objs
.sort((a, b) => {
if (a.side > b.side) {
return -1;
}
if (a.side < b.side) {
return 1;
}
return 0;
})
.forEach((obj) => {
const match = stats.find((stat) => stat.name === obj.code);
const statsIndex = stats.findIndex((stat) => stat.name === obj.code);
if (!match) {
stats = [...stats, { name: obj.code, value: [obj.value] }];
} else {
stats[statsIndex] = {
name: stats[statsIndex].name,
value: [...stats[statsIndex].value, obj.value],
};
}
});
console.log(stats);

You can sort array and use key grouping approach:
const data = [{"teamFK": 8650,"code": "yellow_cards","typeId": 554,"value": "5","side": "home"},{"teamFK": 8650,"code": "goals","typeId": 554,"value": "1","side": "home"},{"teamFK": 8990,"code": "yellow_cards","typeId": 555,"value": "2","side": "away"},{"teamFK": 8990,"code": "goals","typeId": 555,"value": "0","side": "away"}];
const groups = data
.sort(({ side: a }, { side: b }) => b.localeCompare(a))
.reduce((acc, { code, value }) => {
acc[code] ??= { name: code, stats: [] };
acc[code]['stats'].push(value);
return acc;
}, {});
const result = { stats: Object.values(groups) };
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0 }

How to calculate average from nested values in an array using javascript?

I am trying to calculate the average duration for each stage. So in the array below - I should be able to get the average duration for 'test1', which would be 2.
jobs = [
{
"build_id": 1,
"stage_executions": [
{
"name": "test1"
"duration": 1,
},
{
"name": "test2"
"duration": 16408,
},
{
"name": "test3"
"duration": 16408,
},
]
},
{
"build_id": 2,
"stage_executions": [
{
"name": "test1"
"duration": 3,
},
{
"name": "test2"
"duration": 11408,
},
{
"name": "test3"
"duration": 2408,
},
]
}
]
My failed attempt:
avgDuration: function(jobs) {
let durationSum = 0
for (let item = 0; item < this.jobs.length; item++) {
for (let i = 0; i < this.jobs[item].stage.length; item++) {
durationSum += stage.duration
}
durationAverage = durationSum/this.jobs[item].stage.length
}
return durationAverage
What am I doing wrong? I'm not sure how to accomplish this since the duration is spread out between each job.
UPDATE:
This is return a single average for all stages rateher than per stage
<template>
<div class="stages">
<h3>
Average Duration
</h3>
<table>
<tbody>
<tr v-for="item in durations">
<td>
<b>{{ item.average}} {{ item.count }}</b>
// this returns only 1 average and 177 count instead of 10
<br />
</td>
</tr>
</tbody>
</table>
</div>
</template>
<script>
import { calculateDuration } from "../../helpers/time.js";
import { liveDuration } from "../../helpers/time.js";
import moment from "moment";
export default {
name: "Stages",
data() {
return {
jobs: [],
durations: []
};
},
methods: {
avgDuration: function(jobs) {
var averageByName = {}; // looks like { 'name': { average: 111, count: 0 }}
for (var job of jobs) {
for(var stage of job.stage_execution) {
if (averageByName[stage.name] == null) { // we need a new object
averageByName[stage.name] = { average: 0, count: 0 };
}
// just name it so its easier to read
var averageObj = averageByName[stage.name];
// update count
averageObj.count += 1;
// Cumulative moving average
averageObj.average = averageObj.average + ( (stage.duration - averageObj.average) / averageObj.count );
console.log(averageObj.count)
}
}
return averageByName
},
},
created() {
this.JobExecEndpoint =
process.env.VUE_APP_TEST_URL +
"/api/v2/jobs/?limit=10";
fetch(this.JobExecEndpoint)
.then(response => response.json())
.then(body => {
for (let i = 0; i < body.length; i++) {
this.jobs.push({
name: body[i].job.name,
job: body[i].job,
stage_execution: body[i].stage_executions,
});
}
})
.then(() => {
this.$emit("loading", true);
})
.then(() => {
this.durations = this.avgDuration(this.jobs);
})
.catch(err => {
console.log("Error Fetching:", this.JobExecEndpoint, err);
return { failure: this.JobExecEndpoint, reason: err };
});
}
};
</script>

We can do this pretty simply and without overflow from having too many numbers by using a Cumulative moving average and a few loops.
Here is a line the relevant Wikipedia page on Moving Averages and the most relvant formula below.
I will not go into much detail with the above as there are a lot of documents describing this sort of thing. I will however say that the main reason to this over adding all the values together is that there is a far lower chance of overflow and that is why I am using it for this example.
Here is my solution with comments made in code.
var jobs = [ { "build_id": 1, "stage_executions": [ { "name": "test1", "duration": 1, }, { "name": "test2", "duration": 16408, }, { "name": "test3", "duration": 16408, }, ] }, { "build_id": 2, "stage_executions": [ { "name": "test1", "duration": 3, }, { "name": "test2", "duration": 11408, }, { "name": "test3", "duration": 2408, }, ] } ];
var averageByName = {}; // looks like { 'name': { average: 111, count: 0 }}
for (var job of jobs) {
for(var stage of job.stage_executions) {
if (averageByName[stage.name] == null) { // we need a new object
averageByName[stage.name] = { average: 0, count: 0 };
}
// just name it so its easier to read
var averageObj = averageByName[stage.name];
// update count
averageObj.count += 1;
// Cumulative moving average
averageObj.average = averageObj.average + ( (stage.duration - averageObj.average) / averageObj.count );
}
}
// print the averages
for(var name in averageByName) {
console.log(name, averageByName[name].average);
}
Let me know if you have any questions or if anything is unclear.

You could collect the values in an object for each index and map later only the averages.
var jobs = [{ build_id: 1, stage_executions: [{ name: "test1", duration: 1 }, { name: "test2", duration: 16408 }, { name: "test3", duration: 16408 }] }, { build_id: 2, stage_executions: [{ name: "test1", duration: 3 }, { name: "test2", duration: 11408 }, { name: "test3", duration: 2408 }] }],
averages = jobs
.reduce((r, { stage_executions }) => {
stage_executions.forEach(({ duration }, i) => {
r[i] = r[i] || { sum: 0, count: 0 };
r[i].sum += duration;
r[i].avg = r[i].sum / ++r[i].count;
});
return r;
}, []);
console.log(averages.map(({ avg }) => avg));
console.log(averages);
.as-console-wrapper { max-height: 100% !important; top: 0; }

I've used Array.prototype.flatMap to flatten the jobs array into an array of {name:string,duration:number} object. Also, to make more solution a bit more dynamic the function takes in a field argument which returns the average for that specific field.
const jobs = [
{
"build_id": 1,
"stage_executions": [
{
"name": "test1",
"duration": 1,
},
{
"name": "test2",
"duration": 16408,
},
{
"name": "test3",
"duration": 16408,
},
]
},
{
"build_id": 2,
"stage_executions": [
{
"name": "test1",
"duration": 3,
},
{
"name": "test2",
"duration": 11408,
},
{
"name": "test3",
"duration": 2408,
},
]
}
];
const caller = function(jobs, field) {
const filtered = jobs
.flatMap((item) => item.stage_executions)
.filter(item => {
return item.name === field;
})
const total = filtered.reduce((prev, curr) => {
return prev + curr.duration;
}, 0)
return total / filtered.length;
}
console.log(caller(jobs, 'test1'))
console.log(caller(jobs, 'test2'))
console.log(caller(jobs, 'test3'))
In case you get the error flatMap is not a function. You can add this code snippet in your polyfill or at the top of your js file.
Array.prototype.flatMap = function(lambda) {
return Array.prototype.concat.apply([], this.map(lambda));
};
PS: for demostration, I obtained the flatMap implementation from here

Split array into chunk of different size on the basis of their attribute

I have this following array
var array=[{ semster:1, name:Book1 }, { semster:1, name:Book2 }, { semster:2, name:Book4 }, { semster:3, name:Book5 }, { semster:3, name:Book6 }, { semster:4, name:Book7 }]
Now I want to sort my array to split the current array into chunks of array like following
var array=[[{ semster:1, name:Book1 }, { semster:1, name:Book2 }],[ { semster:2, name:Book4 }], [{ semster:3, name:Book5 }, { semster:3, name:Book6 }], [{ semster:4, name:Book7 }]]
I have tried to achieve this with following code :
function splitIntoSubArray(arr, count) {
var newArray = [];
while (arr.length > 0) {
newArray.push(arr.splice(0, count));
}
return newArray;
}
But this can only divide the array on the basis of fixed size. Any kind of suggestion is appreciated.
Thanks

You can simply use Array.reduce() to group items by semester. Object.values() on the map gives you the desired result.
var array=[{ semster:1, name:"Book1" }, { semster:1, name:"Book2" }, { semster:2, name:"Book4" }, { semster:3, name:"Book5" }, { semster:3, name:"Book6" }, { semster:4, name:"Book7" }];
var result = Object.values(array.reduce((a, curr)=>{
(a[curr.semster] = a[curr.semster] || []).push(curr);
return a;
},{}));
console.log(result);

You could reduce the array by checking the last group with the same semester.
var array = [{ semester: 1, name: 'Book1' }, { semester: 1, name: 'Book2' }, { semester: 2, name: 'Book4' }, { semester: 3, name: 'Book5' }, { semester: 3, name: 'Book6' }, { semester: 4, name: 'Book7' }],
grouped = array.reduce((r, o) => {
var last = r[r.length - 1];
if (last && last[0].semester === o.semester) {
last.push(o);
} else {
r.push([o]);
}
return r;
}, []);
console.log(grouped);
.as-console-wrapper { max-height: 100% !important; top: 0; }

How the outer array knows the inner array completed its iteration

In Javascript how the outer array knows the inner array completed its iteration? as I am iterating the below array with recursive function want to know how the outer function or outer array knows the inner array completed the iteration.
{
"rules": [
{
"id": 1,
"value": "ABC"
},
{
"id": 2,
"value": "PQR"
},
{
"id": 3,
"value": "XYZ"
},
{
"rules": [
{
"id": 10,
"value": "ST"
},
{
"id": 12,
"value": "UI"
}
]
},
{
"id": 5,
"value": "5XYZ"
}
]
}
Using the recursive function to iterate the array.
Require the output like
ABC,PQR,XYZ,5XYZ
Within Group ST,UI
Edit1
var message = '';
var infoMessage = getMessageData(false);
function getMessageData(isGroup) {
angular.forEach(rulesArray, function(v, k) {
if (rulesArray.id === undefined) {
message + = getMessageData(true);
} else {
message + = v.value;
if (isGroup) {
message + = 'Within Group' + v.value;
}
}
};
}
}

If I understand correct, you can try something like this:
Idea
Sort array based on objects that have rules and push them back
Loop over array and check
If object has id, concat value to response
If object has rules, use recursion and get response and concat it.
var data = { "rules": [{ "id": 1, "value": "ABC" }, { "id": 2, "value": "PQR" }, { "id": 3, "value": "XYZ" }, { "rules": [{ "id": 10, "value": "ST" }, { "id": 12, "value": "UI" } ] }, { "id": 5, "value": "5XYZ" } ] }
const key = 'rules';
data.rules.sort(function(a,b){
return +(key in a) - +(key in b);
});
function getMessage(obj) {
return obj.reduce(function (p, c, i, a){
if('id' in c) {
p += c.value + (i !== a.length -1 ? ', ': '');
}
if('rules' in c) {
p += getMessage(c.rules);
}
return p;
}, '')
}
console.log(getMessage(data.rules))

You you take a queue for collecting and processing all items of rules with a counter for inserting the group phrase.
function iterate(array) {
var queue = array.slice(),
group = array.length,
temp,
result = '';
while (queue.length) {
temp = queue.shift();
if (temp.rules) {
Array.prototype.push.apply(queue, temp.rules);
continue;
}
if (--group) {
result += (result && ', ') + temp.value;
continue;
}
result += ' Within Group ' + temp.value;
}
return result;
}
var data = { rules: [{ id: 1, value: "ABC" }, { id: 2, value: "PQR" }, { id: 3, value: "XYZ" }, { rules: [{ id: 10, value: "ST" }, { id: 12, value: "UI" }] }, { id: 5, value: "5XYZ" }] };
console.log(iterate(data.rules));