Remove duplicates from array of objects but keep one property as an array

I have a collection like this:

const data = [
{index: 1, number: 's1', uniqId: '123', city: 'LA'},
{index: 2, number: 's2', uniqId: '321', city: 'NY'},
{index: 3, number: 's3', uniqId: '123', city: 'LA'},
{index: 4, number: 's4', uniqId: '111', city: 'TX'},
{index: 5, number: 's5', uniqId: '321', city: 'NY'}
]

I'd like to group it to have below result:

const data = [
{index: 1, numbers: ['s1', 's3'], uniqId: '123', city: 'LA'},
{index: 2, numbers: ['s2', 's5'], uniqId: '321', city: 'NY'},
{index: 3, number: 's4', uniqId: '111', city: 'TX'},
]

I've got a solution but I believe that it can be achieved in a more elegant way. I can use ramda only but preferred is vanilla solution. Here's my solution:

 return Object.values(
    data.reduce((r, e) => {
      const key = `${e.uniqId}|${e.city}`;
      if (!r[key]) {
        r[key] = e;
        if (r[key].numbers && !isEmpty(r[key].numbers)) {
          r[key].numbers.push(e.number);
        } else {
          r[key].numbers = [];
          r[key].numbers.push(e.number);
        }
      } else if (r[key].numbers && !isEmpty(r[key].numbers)) {
        r[key].numbers.push(e.number);
      } else {
        r[key].numbers = [];
        r[key].numbers.push(e.number);
      }
      return r;
    }, {}),
  ).map((item, index) => ({ ...item, index: index }));