Javascript filter object by object with mutation

filter_obj_by_obj.js

const a = [
  {id: 1},
  {id: 4},
  {id: 8},
  {id: 6},
];
const b = [
  {id: 1, op: 'foo'},
  {id: 2, op: 'abc'},
  {id: 3, op: 'def'},
  {id: 4, op: 'ghi'},
  {id: 5, op: 'jkl'},
  {id: 6, op: 'mno'},
  {id: 7, op: 'pqr'},
]
const res = a.reduce((accumulator, objA) => {
  const foundObj = b.find(objB => objB.id === objA.id)
  return foundObj === undefined ? accumulator : [...accumulator, {...objA, raqi: `${foundObj.op} :)`}];
}, []);
console.log(res);
/*
[
  { id: 1, raqi: 'foo :)' },
  { id: 4, raqi: 'ghi :)' },
  { id: 6, raqi: 'mno :)' }
]
*/