Eliminate duplicate array objects

unique_objects.js

const arr = [
  { id: 1, val: 'a' },
  { id: 2, val: 'b' },
  { id: 1, val: 'a' },
  { id: 1, val: 'c' }
  ];

const uni = arr
  .reduce( ( unique, item ) =>
    unique.some( existing => 
        item.id === existing.id
        && item.val === existing.val) 
        ? unique 
        : [...unique, item],
    [] );