Преобразование массива объектов в новую структуру массива

const input = [
    { from: "U20", Id: "1922", to: "U21" },
    { from: "U20", Id: "9338", to: "U21" },
    { from: "U20", Id: "1927", to: "U21" },
    { from: "U20", Id: "1730", to: "U21" }
];

const merged = input.reduce((acc, { from, to, Id }) => {
    const key = `${from}-${to}`;
    acc[key] = acc[key] || { from, to, Ids:[] };
    acc[key]["Ids"].push(Id);
    return acc;
}, {})

const output = Object.values(merged);
console.info(output);

let data = [{
    from: "U20",
    Id: "1922",
    to: "U21"
  },
  {
    from: "U20",
    Id: "9338",
    to: "U21"
  },
  {
    from: "U20",
    Id: "1927",
    to: "U21"
  },
  {
    from: "U20",
    Id: "1730",
    to: "U21"
  }
]


let newData = data.reduce(function(acc, curr) {
  if (acc.hasOwnProperty('from') && acc.from === curr.from) {
    acc.id.push(curr.Id)
  } else {
    acc = {
      from: curr.from,
      id: [curr.Id],
      to: curr.to
    }

  }
  return acc;
}, {});

console.info(newData)

const a = [
  {from: "U20", Id: "1922", to: "U21"},
  {from: "U20", Id: "9338", to: "U21"},
  {from: "U20", Id: "1927", to: "U21"},
  {from: "U20", Id: "1730", to: "U21"},
  {from: "U21", Id: "1745", to: "U22"},
  {from: "U21", Id: "1755", to: "U22"},
]

const f = array => {
  const result = []
  // key-value storage
  const variations = {}
  array.forEach(item => {
    // set storage key
    const key = `${item.from}-${item.to}`;
    // check if key exists
    // if exists use it, if not - create empty array
    variations[key] = variations[key] || []
    // push item ids to storage
    variations[key].push(item.Id)
  })
  Object.keys(variations).map(variation => {
    // deconstruct storage key back to "from" and "to" values
    const [from, to] = variation.split('-');
    const obj = {};
    // write "from" and "to" values
    obj.from = from;
    obj.to = to;
    // add stored values
    obj.ids = variations[variation]
    // save
    result.push(obj)
  })
  console.info(result)
}

f(a)

const entries = [
	{ from: 'U20', to: 'U21', Id: '1922' },
	{ from: 'U20', to: 'U21', Id: '9338' },
	{ from: 'U20', to: 'U21', Id: '1927' },
	{ from: 'U20', to: 'U21', Id: '1730' },
]

const output = entries.reduce((map, {from, to, Id}) =>
{
	if (!map[from])
	{
		map[from] = {}
	}
	
	if (!map[from][to])
	{
		map[from][to] = {from, to, Ids: []}
	}
	
	map[from][to].Ids.push(Id)
	
	return map
}, {})

console.info(output)

var data = [{ from: "U20", Id: "1922", to: "U21" }, { from: "U20", Id: "9338", to: "U21" }, { from: "U20", Id: "1927", to: "U21" }, { from: "U20", Id: "1730", to: "U21" }, { from: "U20", Id: "1730", to: "U22" }, { from: "U21", Id: "1730", to: "U22" }],
    result = Array.from(data
        .reduce(
             (m, { from, to, Id }) =>
                 (k => m.set(k, { from, to, Ids: [...(m.has(k) ? m.get(k).Ids : []), Id] }))
                 ([from, to].join('|')),
             new Map
        )
        .values()
    );

console.info(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

const { flow, groupBy, props, join, map, mergeAllWith, cond, nthArg, eq, concat } = _;

const fn = flow(
  groupBy(flow(                // group by joining from and to as the key
    props(['from', 'to']),
    join('-')
  )),
  map(mergeAllWith(cond([[     // merge all objects in each group
    flow(nthArg(2), eq('Id')), // if the prop name is Id, concat the values
    concat
  ]])))
);

const input = [
    { from: "U20", Id: "1922", to: "U21" },
    { from: "U20", Id: "9338", to: "U21" },
    { from: "U20", Id: "1927", to: "U21" },
    { from: "U20", Id: "1730", to: "U21" }
];

const result = fn(input);

console.info(result);

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