robjez February 2016

Flattening deeply nested array of objects

I got following data structure, which is an array of accounts objects, where some accounts are being parents to its children accounts, which in turn can be parents to other accounts etc.:

[{
  "id": "acc.1260446672222.11",
  "type": "EXPENSES_FOLDER",
  "name": "Expense Group",
  "balance": 3418.11,
  "children": [{
    "id": "acc.1260446672238.27",
    "type": "EXPENSE",
    "name": "Advertising, Promotion and Entertainment Account",
    "balance": 0,
    "children": []
  }, {
    "id": "acc.9a2492ba-0d82-4f4a-a1b4-14868f1e1a39",
    "type": "EXPENSES_FOLDER",
    "name": "Premises Costs",
    "balance": 0,
    "children": [{
      "id": "acc.287ba5b6-5536-428b-950f-d71d2af73ccc",
      "type": "EXPENSE",
      "name": "Use of Home - Gas",
      "balance": 0,
      "children": [

      ]
    }, {
      "id": "acc.7091ee15-3f02-4bd1-94e5-5918cf986969",
      "type": "EXPENSE",
      "name": "Hire of Venue, Studios, Teaching Rooms",
      "balance": 0,
      "children": [

      ]
    }]
  }, {
    "id": "acc.827ec446-edeb-4f2b-8032-d306292d2d83",
    "type": "EXPENSES_FOLDER",
    "name": "Administrative Expenses",
    "balance": 558.61,
    "children": [{
      "id": "acc.0ed5fc81-7734-4452-86a9-db22a6b0f8e8",
      "type": "EXPENSE",
      "name": "Bank Charges",
      "balance": 15,
      "children": [

      ]
    }, {
      "id": "acc.e2cdb2c0-8565-4991-a35a-d4596b0ddf45",
      "type": "EXPENSE",
      "name": "Software & Computer Peripherals",
      "balance": 417.13,
      "children": [

      ]
    }, {
      "id": "acc.96d5d00e-43f4-4d3a-b97b-fdf258c65514",
      "type": "EXPENSE",
      "name": "Printing, photocopying etc",
      "balance": 55.93,
      "children": [

      ]
    }, {
      "id": "acc.494dd64a-4fb3-42b8-be3e-8f3b59a2ef59",
      "type": "EXPENSE",
      "name": "Artists Administration Service",
      "balance": 0,
      "children": [

      ]
    }, {
      "id": "acc.12604466        

Answers


Dustin Poissant February 2016

You could make a recursive function that looks through each account, and if it has children calls itself on the children, the function should return a flattened array of accounts.

This example is a bit more complicated than it has to be because I am assuming that order matters and that the parent should be before the children.

function flattenAccounts(accounts){
  var a = [];
  for(var i=0;i<accounts.length;i++){
    var o = accounts[i];
    if(o.children){
      var c = flattenAccounts(o.children);
      if(c){
          a = a.concat(c);
      }
    }
    a.push(o)
  }
  return a;
}

This is a simpler example but the children would end up before the parent.

function flattenAccounts(accounts){
  var a = [];
  for(var i=0;i<accounts.length;i++){
    if(accounts[i].children){
      a = a.concat(flattenAccounts(accounts[i].children) )
    }
    a.push(accounts[i])
  }
  return a;
}


Thomas February 2016

try to understand this version, with it's benefits and implications

function flatten(into, node){
    if(node == null) return into;
    if(Array.isArray(node)) return node.reduce(flatten, into);
    into.push(node);
    return flatten(into, node.children);
}

var out = flatten([], yourArray);

the argument order might be confusing at first, unless you are used to reduced, or the concept of options first, data last, wich is very handy when it comes to FP and currying or partial application.


Nina Scholz February 2016

Just iterate over and if a children is found get the array from the children concatinated.

function flat(array) {
    var result = [];
    array.forEach(function (a) {
        result.push(a);
        if (Array.isArray(a.children)) {
            result = result.concat(flat(a.children));
        }
    });
    return result;
}

var data = [{ id: "acc.1260446672222.11", type: "EXPENSES_FOLDER", name: "Expense Group", balance: 3418.11, children: [{ id: "acc.1260446672238.27", type: "EXPENSE", name: "Advertising, Promotion and Entertainment Account", balance: 0, children: [] }, { id: "acc.9a2492ba-0d82-4f4a-a1b4-14868f1e1a39", type: "EXPENSES_FOLDER", name: "Premises Costs", balance: 0, children: [{ id: "acc.287ba5b6-5536-428b-950f-d71d2af73ccc", type: "EXPENSE", name: "Use of Home - Gas", balance: 0, children: [] }, { id: "acc.7091ee15-3f02-4bd1-94e5-5918cf986969", type: "EXPENSE", name: "Hire of Venue, Studios, Teaching Rooms", balance: 0, children: [] }] }, { id: "acc.827ec446-edeb-4f2b-8032-d306292d2d83", type: "EXPENSES_FOLDER", name: "Administrative Expenses", balance: 558.61, children: [{ id: "acc.0ed5fc81-7734-4452-86a9-db22a6b0f8e8", type: "EXPENSE", name: "Bank Charges", balance: 15, children: [] }, { id: "acc.e2cdb2c0-8565-4991-a35a-d4596b0ddf45", type: "EXPENSE", name: "Software & Computer Peripherals", balance: 417.13, children: [] }, { id: "acc.96d5d00e-43f4-4d3a-b97b-fdf258c65514", type: "EXPENSE", name: "Printing, photocopying etc", balance: 55.93, children: [] }, { id: "acc.494dd64a-4fb3-42b8-be3e-8f3b59a2ef59", type: "EXPENSE", name: "Artists Administration Service", balance: 0, children: [] }, { id: "acc.1260446672238.35", type: "EXPENSE", name: "Stationery", balance: 0, children: [] }, { id: "acc.96d89d0d-5465-488b-b37f-d41ca114c5e6", type: "EXPENSE", name: "Mobile Telephone", bala 

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Asked in February 2016
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