const dataArray = [
  {
    id: 1,
    odds: 1.28,
  },
  {
    id: 15,
    odds: 2.52,
  }
];

const convertedData = dataArray.reduce((result, obj) => {
  result[obj.id.toString()] = { ...obj };
  return result;
}, {});

console.log(convertedData);