I have an array of objects that looks like this:
[
{external_id: 1, items: [{k: 'v'}] },
{external_id: 2, items: [{k1: 'v1'}] },
{external_id: 1, items: [{k2: 'v2'}, {k3: 'v3'}] }
]
What I want to do is merge nested arrays based on external_id and return 'clean array' which will look like this:
[
{external_id: 1, items: [{k: 'v'}, {k2: 'v2'}, {k3: 'v3'}] },
{external_id: 2, items: [{k1: 'v1'}] }
]
So my question is what is the clean way to achieve that without using classic for-loop ?
You will have to loop. You can choose to loop with for, forEach, map, reduce, find, ...etc, but you'll have to loop.
Here is a way that creates a Map keyed by the external_id, and then populates that map with the items. Finally the values of that map represent the result:
let data = [{external_id: 1, items: [{k: 'v'}] },{external_id: 2, items: [{k1: 'v1'}] },{external_id: 1, items: [{k2: 'v2'}, {k3: 'v3'}] }];
let map = new Map(data.map(({external_id}) => [external_id, { external_id, items:[] }]));
data.forEach(o => map.get(o.external_id).items.push(...o.items));
let result = [...map.values()];
console.log(result);Collected from the Internet
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