Merge array of objects by nested property ID

Question

This is my example:

{
    id: 'productId',
    label: 'productLabel',
    items: productSizes.map( productSize => {
        return {
            id: productSize.groupId,
            label: productSize.groupId.split('-')[0],
            items: productSize.size,
        }
    }),
}

This would result in something like this with our data:

{
    id: 'productId',
    label: 'productLabel'
    items: [
        {id: 'productA-11', label: 'productA', items: {width: 100, height: 100}},
        {id: 'productA-11', label: 'productA', items: {width: 150, height: 150}},
        {id: 'productA-11', label: 'productA', items: {width: 200, height: 200}},
        {id: 'productB-22', label: 'productB', items: {width: 100, height: 100}},
    ]
}

But I would like to get something like this:

{
    id: 'productId',
    label: 'productLabel'
    items: [
        {id: 'productA-11', label: 'productA', items: [ {width: 100, height: 100}, {width: 150, height: 150}, {width: 200, height:200}],
        {id: 'productB-22', label: 'productB', items: [{width: 100, height: 100}],
    ]
}

Not sure if I described my problem well with words, but I would like to somehow flatten the inner property items, so that sizes of the SAME productId would be merged into a single array.

@Nitheesh I have no code as I have no clue how to start with tackling this issue. — Nightcorey
– Nightcorey, Commented Nov 17, 2021 at 9:57

Nitheesh · Accepted Answer · 2021-11-17 10:12:14Z

1

Array.reduce will help you

Logic

Loop throughthe items array of your object.
Check if the accumulator of the reducer already have an item with same id and label
It there is a node with same id and label, push the current item to the items array of that node else insert a new node to the accumulator with id, label and items

Working Fiddle

const data = {
  id: 'productId',
  label: 'productLabel',
  items: [
    { id: 'productA-11', label: 'productA', items: { width: 100, height: 100 } },
    { id: 'productA-11', label: 'productA', items: { width: 150, height: 150 } },
    { id: 'productA-11', label: 'productA', items: { width: 200, height: 200 } },
    { id: 'productB-22', label: 'productB', items: { width: 100, height: 100 } },
  ]
};
const { id, label } = data;
const items = data.items.reduce((acc, curr) => {
  const node = acc.find(item => item.id === curr.id && item.label === curr.label);
  if (node) {
    node.items.push(curr.items);
  } else {
    acc.push({
      id: curr.id,
      label: curr.label,
      items: [curr.items]
    })
  }
  return acc;
}, [])
const output = {
  id,
  label,
  items,
}
console.log(output);

answered Nov 17, 2021 at 10:12

Nitheesh

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1 Comment

Nightcorey Over a year ago

Thank you Nitheesh, it works. I thought about array.reduce(), but never understood it really well.

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