1const array =
2  [
3    { "name": "Joe", "age": 17 },
4    { "name": "Bob", "age": 17 },
5    { "name": "Carl", "age": 35 }
6  ]
7
8const key = 'age';
9
10const arrayUniqueByKey = [...new Map(array.map(item =>
11  [item[key], item])).values()];
12
13console.log(arrayUniqueByKey);
14
15   /*OUTPUT
16       [
17        { "name": "Bob", "age": 17 },
18        { "name": "Carl", "age": 35 }
19       ]
20   */
21
22 // Note: this will pick the last duplicated item in the list.

1const data = [
2  { group: 'A', name: 'SD' }, 
3  { group: 'B', name: 'FI' }, 
4  { group: 'A', name: 'MM' },
5  { group: 'B', name: 'CO'}
6];
7const unique = [...new Set(data.map(item => item.group))]; // [ 'A', 'B']

1//ES6
2let array = [
3  { "name": "Joe", "age": 17 },
4  { "name": "Bob", "age": 17 },
5  { "name": "Carl", "age": 35 }
6];
7array.map(item => item.age)
8  .filter((value, index, self) => self.indexOf(value) === index)
9
10> [17, 35]

1const unique = [...new Set(array.map(item => item.age))];

1function toUniqueArray(a){
2    var newArr = [];
3    for (var i = 0; i < a.length; i++) {
4        if (newArr.indexOf(a[i]) === -1) {
5            newArr.push(a[i]);
6        }
7    }
8  return newArr;
9}
10var colors = ["red","red","green","green","green"];
11var colorsUnique=toUniqueArray(colors); // ["red","green"]

1function unique(array, propertyName) {
2   return array.filter((e, i) => array.findIndex(a => a[propertyName] === e[propertyName]) === i);
3}
4