ES6 remove dup in an array of object by checking `id` property

arr.js

/***
 * Initial array
 ***/

const arr = [{
  name: 'A',
  id: 1
}, {
  name: 'B',
  id: 2
}, {
  name: 'C',
  id: 3
}];

/***
 * Append to array
 ***/

const newArr = [].concat(...[arr, [{
  name: 'D',
  id: 3
}, {
  name: 'E',
  id: 4
}, {
  name: 'F',
  id: 5
}, {
  name: 'G',
  id: 6
}, {
  name: 'H',
  id: 7
}]]);

/***
 * Remove dup by checking `id` property
 ***/

const removeDup = newArr.filter((elem, index, self) => self.findIndex(elemIndex => elemIndex.id === elem.id) === index);