Group by Object ID's in Javascript

Question

I have an array of ID's and organizations like so:

var ids = ['1','2', '3'];
var orgs =
    [ 
      { name: "Org 1", id: 1 },
      { name: "Org 2", id: 2 },
      { name: "Org 3", id: 2 }
    ]

I want to loop through these to output something like this:

{
    1: [
        {name: "Org 1", id: 1}
    ],
    2: [
        {name: "Org 2", id: 2},
        {name: "Org 3", id: 2}
    ]
}

I tried this without success:

var results = orgs.forEach(function (org) {
    if (results[org.id]) {
        results.push(org)
    } else {
        results[org.id] = [org]
    };
});

Your results is an invalid structure. { [ ] } is invalid, you can't have an object without keys. — gen_Eric
– gen_Eric, Commented Dec 3, 2014 at 20:56

Scott Sauyet · Accepted Answer · 2014-12-03 21:18:56Z

11

If you don't want to use a library like Underscore, Ramda, or Lo-Dash, then it's simple enough to write this using reduce:

var results = orgs.reduce(function(results, org) {
    (results[org.id] = results[org.id] || []).push(org);
    return results;
}, {})

edited Dec 3, 2014 at 21:18

answered Dec 3, 2014 at 21:05

Scott Sauyet

50.9k5 gold badges57 silver badges111 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Anthony Over a year ago

Thanks Scott - exactly what I'm searching for.

Scott Sauyet Over a year ago

But notice that libraries also make this easy. With Ramda you could just do R.groupBy(R.prop('id'), orgs);. And if you wanted a reusable function, it would just be var groupById = R.groupBy(R.prop('id'));. Lo-Dash and Underscore offer fairly similar functionality.

Headless Over a year ago

Slightly newer syntax var results = orgs.reduce((results, org) => ({...results, [org.id]: org}), {})

Scott Sauyet Over a year ago

@Headless: that will only allow one entry per key. The question requests an array of them, and in fact, "2" will have two entries in the sample data.

Philipp Kyeck · Accepted Answer · 2019-12-12 09:49:53Z

1

you should use underscore and just return your id

http://underscorejs.org/#groupBy

_.groupBy([1.3, 2.1, 2.4], function(num){ return Math.floor(num); });
// => {1: [1.3], 2: [2.1, 2.4]}

you might also want to take a look at lo-dash

edited Dec 12, 2019 at 9:49

Philipp Kyeck

18.9k20 gold badges90 silver badges126 bronze badges

answered Dec 3, 2014 at 21:02

Andrew Clark

1,4331 gold badge10 silver badges16 bronze badges

Collectives™ on Stack Overflow

Group by Object ID's in Javascript

2 Answers 2

4 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related