Cacher is the code snippet organizer for pro developers

const docs = [
    {
      "parkingArealId": "swgh2dds61q5"
    },
    {
      "parkingArealId": "swgh2dds61q5"
    },
    {
      "parkingArealId": "swgh2dds61q5"
    },
    {
      "parkingArealId": "swgh2dds61q5"
    },
 	{
      "parkingArealId": "twgh2dds61q5"
    },
    {
      "parkingArealId": "twgh2dds61q5"
    }
  ];
function getUnique(arr, comp) {

  const unique = arr
       .map(e => e[comp])

     // store the keys of the unique objects
    .map((e, i, final) => final.indexOf(e) === i && i)

    // eliminate the dead keys & store unique objects
    .filter(e => arr[e]).map(e => arr[e]);

   return unique;
}

console.log(getUnique(docs,'parkingArealId'));