How to get distinct value from an array of objects containing array

December 20, 2021

I am trying to get an array of distinct values from the data structure below. I tried using reduce and object keys with no luck. Can somebody please point me in the right direction?

Data:

var data = [{
    "id": 1,
    "Technologies": ["SharePoint", "PowerApps"]
  },
  {
    "id": 2,
    "Technologies": ["SharePoint", "PowerApps", "SomethingElse"]
  },
  {
    "id": 3,
    "Technologies": ["SharePoint"]
  },
  {
    "id": 4,
    "Technologies": ["PowerApps"]
  },
  {
    "id": 5,
    "Technologies": null
  }
]

Finished result should look like:

var distintValues = ["PowerApps", "SharePoint", "SomethingElse", null]

My attempt:
https://codepen.io/bkdigital/pen/MWEoLXv?editors=0012

>Solution :

You could use .flatMap() with a Set. .flatMap allows you to map each object’s technology to one resulting array, and the Set allows you to remove the duplicates. With the help of optional chaining ?., you can also keep the null value (so it doesn’t throw when accessing Technologies) like so:

const data = [{ "id": 1, "Technologies": ["SharePoint", "PowerApps"] }, { "id": 2, "Technologies": ["SharePoint", "PowerApps", "SomethingElse"] }, { "id": 3, "Technologies": ["SharePoint"] }, { "id": 4, "Technologies": ["PowerApps"] }, { "id": 5, "Technologies": null } ];

const res = [...new Set(data.flatMap(obj => obj?.Technologies))];
console.log(res);