How to get unique values from an array of objects in JavaScript, but filtered by certain value

Question

I would like to extend the question that has been asked some time ago: How to get distinct values from an array of objects in JavaScript?

my case is very similar: I have the following:

var array = 
    [
        {"name":"Doctor", "age":17}, 
        {"name":"Doctor", "age":17},
        {"name":"Doctor", "age":18},
        {"name":"Nurse", "age":17}, 
        {"name":"Nurse", "age": 35}
        {"name":"Nurse", "age": 35}
    ]

What is the best way to be able to get an array of all of the distinct ages, but for chosen speciality such that I get an result array of:

filter by doctor parameter: [17, 18]

filter by nurse parameter: [17, 35]

do you mean just filter first and then apply something like: `array.map(item => item.age) .filter((value, index, self) => self.indexOf(value) === index)` — gileneusz, Aug 14 '22 at 10:52
I'd like to know what med-school hands out medical degrees to high-school kids... — Dai, Aug 14 '22 at 10:53

score 2 · Accepted Answer · answered Aug 14 '22 at 10:52

Use array functions

const array = [{
    "name": "Doctor",
    "age": 17
  },
  {
    "name": "Doctor",
    "age": 18
  },
  {
    "name": "Nurse",
    "age": 17
  },
  {
    "name": "Nurse",
    "age": 35
  }
]

console.log(getUniqueAges(array, 'Doctor'))
console.log(getUniqueAges(array, 'Nurse'))

function getUniqueAges(data, name) {
  return [...new Set(data
    .filter(datum => datum.name === name)
    .map(datum => datum.age))]
}

score 1 · Answer 2 · answered Aug 14 '22 at 10:58

1

just like in the answer you linked, but you filter (the example below is filtered by name==="doctor) the array before you pass it to the Set:

const data =     [
    {"name":"Doctor", "age":17}, 
    {"name":"Doctor", "age":18},
    {"name":"Nurse", "age":17}, 
    {"name":"Nurse", "age": 35}
];
const unique = [...new Set(data.filter(item => item.name === "doctor").map(item => item.age))]; // [ '17', '18']

answered Aug 14 '22 at 10:58

DaveExotic

115
7

your solution works well, but was second, so I can give you only the point up – gileneusz Aug 14 '22 at 11:04

How to get unique values from an array of objects in JavaScript, but filtered by certain value

2 Answers2