#!/usr/local/bin/node
const test1 = [
{
  id: 1,
  service: 'A',
},
{
  id: 2,
  service: 'B',
},
{
  id: 3,
  service: null,
},
{
  id: 4,
  service: 'D',
}
];

const test2 = test1.map((val) => {
  return val.service;
});

console.log(test2, test2.indexOf(null));