merge an array of objects where one property is the same, while transferring the unique values of another property into an array

Question

I have an array of objects in which most of the properties may be duplicates of each other, but one value may differ:

const originalArray = [
  { id: 1, name: 'x', 'description': 'x', url: 'y' },
  { id: 2, name: 'x', 'description': 'x', url: 'z' }
]

I want to dedupe this array based on a difference of name, but retain the URL differences as an array in the deduped array:

const dedupedArray = [
  { id: 1, name: 'x', 'description': 'x', url: ['y','z'] },
]

function removeDuplicatesByProperty(keyFn, array) {
  const mySet = new Set();
  return array.filter(function (x) {
    const key = keyFn(x),
      isNew = !mySet.has(key);
    if (isNew) mySet.add(key);
    return isNew;
  });
}

const dedupedArray = removeDuplicatesByProperty((x) => x.name, originalArray);

Answer 1

You can use Array.reduce :

 const originalArray = [ { id: 1, name: 'x', 'description': 'x', url: 'y' }, { id: 2, name: 'x', 'description': 'x', url: 'z' } ] const res = originalArray.reduce((a,b) => { const found = a.find(e => e.name == b.name); return found ? found.url.push(b.url) : a.push({...b, url:[b.url]}), a; }, []) console.log(res)

Answer 2

Reduce the array to a Map, and merge duplicates using a mergeFn . Convert the Map.values() iterator back to an array using Array.from() or array spread:

 const originalArray = [ { id: 1, name: 'x', 'description': 'x', url: 'y' }, { id: 2, name: 'x', 'description': 'x', url: 'z' } ] const dedupeMerge = (keyFn, mergeFn, array) => Array.from( array.reduce((acc, o) => { const key = keyFn(o); if(!acc.has(key)) return acc.set(key, o); return acc.set(key, mergeFn(acc.get(key), o)); }, new Map()).values() ); const dedupedArray = dedupeMerge( x => x.name, (o1, o2) => ({ ...o1, url: [o1.url, o2.url].flat() }), originalArray ); console.log(dedupedArray);