Javascript unique array items

Question

I have an array like this:

var data = [
            { Group: 'A', Name: 'SD' },
            { Group: 'B', Name: 'FI' },
            { Group: 'A', Name: 'MM' },            
            { Group: 'B', Name: 'CO' }
           ];

I want to get only the unique Group values in an array like:

var unique = ['A','B'];

I looked at some of the examples on SO but I don't understand them. Can anyone tell me how I should do this?

Petar Ivanov · Accepted Answer · 2011-11-08 04:38:04Z

2

var data = [
             { Group: 'A', Name: 'SD' },
             { Group: 'B', Name: 'FI' },
             { Group: 'A', Name: 'MM' },            
             { Group: 'B', Name: 'CO' }
           ];

var set = {};
for (var i = 0; i < data.length; i++)
    set[data[i].Group] = 1;

var arr = [];
for(var key in set)
    arr.push(key);

alert(arr);

edited Nov 8, 2011 at 4:38

answered Nov 7, 2011 at 4:07

Petar Ivanov

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5 Comments

Raynos Over a year ago

Replace that loop with arr = Object.keys(set)

Cheran Shunmugavel Over a year ago

FYI, Object.keys is new in ECMAScript 5, so it may not be available in all browsers (reference)

user686924 Over a year ago

@PetarIvanov This works great in IE9. As per Cheran's FYI, this will not work in IE < 9. Any suggestion on how I should this without Object.keys() ?

KooiInc Over a year ago

@user686924: see developer.mozilla.org/en/JavaScript/Reference/Global_Objects/…

Petar Ivanov Over a year ago

@user686924: I reverted back to my original solution, which doesn't use Object.keys

Vlad Bezden · Accepted Answer · 2016-01-29 19:23:31Z

0

If you are using ES6/ES2015 or later you can do it this way:

var unique = [...new Set(data.map(item => item.Group))];

Here is an example on how to do it.

answered Jan 29, 2016 at 19:23

Vlad Bezden

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