javascript getting in array all different values for a key in array of objects

Question

I need to obtain from a given array of objects, all different values for a given key. Example:

 var arr =   [
      {
        "cod": 0
        "level": "INF"
      },{
        "cod": 1
        "level": "INF"
      },{
        "cod": 2
        "level": "INC"
      },{
        "cod": 3
        "level": "IND"
      }
]

different_values(arr,'level')

should return:

['INF','INC','IND']

WHat would be an easy way to achieve so?

Barmar · Accepted Answer · 2015-04-09T10:37:53.530

Loop over the array and get the specified property from each element. use them as the keys in an object to get rid of the duplicates, and then return the keys of that object.

var arr =   [
      {
        "cod": 0,
        "level": "INF"
      },{
        "cod": 1,
        "level": "INF"
      },{
        "cod": 2,
        "level": "INC"
      },{
        "cod": 3,
        "level": "IND"
      }
];
function different_values(array, property) {
    var values_seen = {}; // for removing duplicates
    for (var i = 0; i < array.length; i++) {
        values_seen[array[i][property]] = true;
    }
    return Object.keys(values_seen);
}
alert(JSON.stringify(different_values(arr, 'level')));

Yeah, I like this method of deduping. – Andy Apr 09 '15 at 10:37 — Andy, Apr 09 '15 at 10:37

score 2 · Answer 2 · answered Apr 09 '15 at 10:37

2

function different_values(arr, value){
    var res = [];
    for(var i=arr.length;i--;){
        if(res.indexOf(arr[i][value]) === -1){
            res.push(arr[i][value])
        }
    }
    return res;
}

DEMO https://jsfiddle.net/mdzLr4q6/1/

answered Apr 09 '15 at 10:37

Mihail

1,469
11
13

Omar Elawady · Answer 3 · 2015-04-09T10:47:04.227

0

try this:

function different_values(arr,key){
    var diff=[];
    for(var i = 0;i < arr.length;i++){
        var k=arr[i][key];
        if(diff.indexOf(k)===-1)diff.push(k);
    }
    return diff;
}

edited Apr 09 '15 at 10:47

answered Apr 09 '15 at 10:33

Omar Elawady

3,300
1
13
17

2

You should avoid using `for in` loops for arrays. `for (var i = 0, l = arr.length; i < l; i++)` would be better. Plus you get to cache the length of the array. – Andy Apr 09 '15 at 10:39
why should I avoid it ? – Omar Elawady Apr 09 '15 at 10:43
http://stackoverflow.com/questions/500504/why-is-using-for-in-with-array-iteration-such-a-bad-idea – Andy Apr 09 '15 at 10:44

score -1 · Answer 4 · answered Apr 09 '15 at 10:33

-1

function different_values(array, key) {

    var count = array.length,
        output = [];

    for (var i = 0; i < count; i++) {
        output.push(array[i][key]);
    }

    return output;
}

answered Apr 09 '15 at 10:33

Vigneswaran Marimuthu

2,452
13
16

You're not removing duplicates from the output array which is what the OP wants. – Andy Apr 09 '15 at 11:26
Oops didn't notice the word "different" – Vigneswaran Marimuthu Apr 09 '15 at 11:34

Thalsan · Answer 5 · 2015-04-09T11:58:42.660

Just loop through the objects in a for loop and push the level in a result array.

Edit: added indexOf to get unique values

function different_values (arr, key) {
    var result = [];

    for (var i in arr) {
        if (result.indexOf(arr[i][key]))            
            result.push(arr[i][key]);
    }

    return result;
}

Make sure to correct your objects. You are missing a comma between the elements:

{
    "cod": 0
    "level": "INF"
}

should be:

{
    "cod": 0,
    "level": "INF"
}

javascript getting in array all different values for a key in array of objects

5 Answers5