What is the recommended way to filter Objects with Unique property in the array in JS?

Question

How to filter objects in array based on unique property here i have an array where KEY is the key value in the objects. How to filter the objects where key value is unique. Key

Answer 1

You can iterate over the members and look at the KEY property. If it's not been seen before, add it to a list of seen keys and return true. If it has been seen before, return false. E.g.

var array = [{
  "KEY": "00001",
  "ID": "1234",
  "ID_DESC": "1234",
  "NOT_UNIQUE_VALUE": "119.0",
  "NOT_UNIQUE_TYPE": "this is not unique"
}, {
  "KEY": "00001",
  "ID": "1234",
  "ID_DESC": "1234",
  "NOT_UNIQUE_VALUE": "11019.0",
  "NOT_UNIQUE_TYPE": "not unique type"
}, {
  "KEY": "00002",
  "ID": "2468",
  "ID_DESC": "2468",
  "NOT_UNIQUE_VALUE": "195.0",
  "NOT_UNIQUE_TYPE": "not unique type",
}, {
  "KEY": "00002",
  "ID": "2468",
  "ID_DESC": "2468",
  "NOT_UNIQUE_VALUE": "195.0",
  "NOT_UNIQUE_TYPE": "not unique type",
}]

var seenKeys = Object.create(null);
var result = array.filter(function(obj) {
  return seenKeys[obj.KEY]? false : seenKeys[obj.KEY] = true;
});

console.log(result)

As an arrow function:

var seenKeys = Object.create(null);
var result = array.filter(obj => seenKeys[obj.KEY]? false : seenKeys[obj.KEY] = true);