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.

Answer 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);