JavaScript conditional array refactor

Question

Lets say I have an array like this :

myArray = 
[
 {
  combineNext: false,
  title: 'Title1',
  items: [{item1},{item2}] 
 }, 
 {
  combineNext: true,
  title: 'Title2',
  items: [{item3}] 
 },
 {
  combineNext: true
  title: 'Title3',
  items: [{item4},{item5}] 
 },
 {
  combineNext: false
  title: 'Title4',
  items: [{item6}] 
 },
 {
  combineNext: true
  title: 'Title5',
  items: [{item7},{item8},{item9}] 
 }
]

I need to check where combineNext is true and concat the next array item (if exists) to it to create a new array of arrays like this:

theNewArrayofArrays = 
[
 [
  {
  combineNext: false,
  title: 'Title1',
  items: [{item1},{item2}] 
  }
 ], 
 [
  {
   combineNext: true,
   title: 'Title2',
   items: [{item3}] 
  },
  {
   combineNext: true
   title: 'Title3',
   items: [{item4},{item5}] 
  },
  {
   combineNext: false
   title: 'Title4',
   items: [{item6}] 
  },
 ],
 [
  {
   combineNext: true
   title: 'Title5',
   items: [{item7},{item8},{item9}] 
  }
 ]
]

What is the best way to have this output ?

I will map on the array of arrays after that so i will have 3 lists — toufek khoury
– toufek khoury, Commented Feb 20, 2018 at 18:10

Nenad Vracar · Accepted Answer · 2018-02-20 18:10:38Z

4

You can do this with reduce method and check previous element. If the previous element has combineNext true you add current element to last element in accumulator otherwise you push new array.

const myArray = [{"combineNext":false,"title":"Title1"},{"combineNext":true,"title":"Title2"},{"combineNext":true,"title":"Title3"},{"combineNext":false,"title":"Title4"},{"combineNext":true,"title":"Title5"}]

const result = myArray.reduce((r, e, i, arr) => {
  const prev = arr[i - 1];
  if (prev && prev.combineNext) r[r.length - 1].push(e)
  else r.push([e])
  return r;
}, [])

console.log(result)

answered Feb 20, 2018 at 18:10

Nenad Vracar

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