data.js

let firstCollection = [
  {id: 1, name: 'dog', item_id: 47},
  {id: 2, name: 'truck', item_id: 38},
  {id: 3, name: 'martian', item_id: 123}
];

let secondCollection = [
  {id: 123, name: 'martian'}
];

differenceWith.js

let unusedItems = _.differenceWith(firstCollection, secondCollection, (firstItem, secondItem) => {
  return firstItem.id === secondItem.item_id;
});

// => [{id: 1, name: 'dog', item_id: 47}, {id: 2, name: 'truck', item_id: 38}]

looping.js

let unusedItems = _.reject(firstCollection, (firstItem) => {
  let isDuplicate;

  secondCollection.forEach((secondItem) => {
    if (firstItem.id === secondItem.item_id) {
      isDuplicate = true;
    }
  });
  
  return isDuplicate;
});

// => [{id: 1, name: 'dog', item_id: 47}, {id: 2, name: 'truck', item_id: 38}]