const array =
[
{ "name": "Joe", "age": 17 },
{ "name": "Bob", "age": 17 },
{ "name": "Carl", "age": 35 }
]
const key = 'age';
const arrayUniqueByKey = [...new Map(array.map(item =>
[item[key], item])).values()];
console.log(arrayUniqueByKey);
/*OUTPUT
[
{ "name": "Bob", "age": 17 },
{ "name": "Carl", "age": 35 }
]
*/
// Note: this will pick the last duplicated item in the list.