title: ES6 - Distinct elements based on two keys
body: <p>In the following array, there is duplicate elements (with same dates and ids)</p>
  
  <pre><code>[{date: "2018-02-20", id: "ccff5cae-0d38-450d-90f9-2490256db84c"},
  {date: "2018-02-21", id: "8ffc7266-6a19-40a7-b181-7c7d73be8467"},
  {date: "2018-02-22", id: "147afdd1-8c8b-4fde-b992-d8d8465a1771"},
  {date: "2018-02-23", id: "72f10683-17a5-49d1-9e78-5fc2b380a314"},
  {date: "2018-02-24", id: "2d2cd12c-2472-4e1d-96c9-84d8a0df1eda"},
  {date: "2018-03-05", id: "5daf20a7-7106-419d-9761-3e96dfedf5ff"},
  {date: "2018-03-08", id: "4bbcc474-ff88-4fc0-aede-abde0ae42b93"},
  {date: "2018-03-08", id: "2a883953-df6a-45b1-9e0a-eb67cc1752b3"},
  {date: "2018-03-08", id: "578b78cb-6d2c-4e91-a5a1-6d081945a51b"},
  {date: "2018-03-09", id: "defb35e5-1a43-4347-ac4b-a85093551900"},
  {date: "2018-02-20", id: "ccff5cae-0d38-450d-90f9-2490256db84c"},
  {date: "2018-02-21", id: "8ffc7266-6a19-40a7-b181-7c7d73be8467"},
  {date: "2018-02-22", id: "147afdd1-8c8b-4fde-b992-d8d8465a1771"},
  {date: "2018-02-23", id: "72f10683-17a5-49d1-9e78-5fc2b380a314"},
  {date: "2018-02-24", id: "2d2cd12c-2472-4e1d-96c9-84d8a0df1eda"},
  {date: "2018-03-05", id: "5daf20a7-7106-419d-9761-3e96dfedf5ff"},
  {date: "2018-03-08", id: "4bbcc474-ff88-4fc0-aede-abde0ae42b93"},
  {date: "2018-03-08", id: "2a883953-df6a-45b1-9e0a-eb67cc1752b3"},
  {date: "2018-03-08", id: "578b78cb-6d2c-4e91-a5a1-6d081945a51b"},
  {date: "2018-03-09", id: "defb35e5-1a43-4347-ac4b-a85093551900"},]
  </code></pre>
  
  <p>What is the best way (in ES6) to remove duplicates?</p>