How can I perform an inner join with two object arrays in JavaScript?

Question

I have two object arrays:

var a = [
  {id: 4, name: \'Greg\'},
  {id: 1, name: \'David\'},
  {id: 2, name: \'John\'},
  {id: 3, name: \'Matt\'},
]

var b = [         


        

Answer 1

One of the ways how to solve it.

const a = [
  {id: 4, name: 'Greg'},
  {id: 1, name: 'David'},
  {id: 2, name: 'John'},
  {id: 3, name: 'Matt'},
];

const b = [
  {id: 5, name: 'Mathew', position: '1'},
  {id: 6, name: 'Gracia', position: '2'},
  {id: 2, name: 'John', position: '2'},
  {id: 3, name: 'Matt', position: '2'},
];

const r = a.filter(({ id: idv }) => b.every(({ id: idc }) => idv !== idc));
const newArr = b.concat(r).map((v) => v.position ? v : { ...v, position: null });

console.log(newArr);