Reordering array objects via javascript

Question

I have been doing some sorting and still dont get it why the result is []. could you guys help me out what im missing?

I have my raw array object:

var data = [
 {message:'hello', username:'user1'},
 {message:'data', username:'user1'},
 {message:'sample', username:'user2'},
 {message:'here', username:'user2'},
];

my function is:

var chat = [];
function reorder(obj) {
    obj.forEach( function(val, i) {
        if(typeof chat[val.username] === 'undefined') {
            chat[val.username] = [];
            chat[val.username].push(val);   
        }
        else 
            chat[val.username].push(val);
    });
    return chat;
}

and on my console:

reorder(data);

I am expecting to have:

var data2 = [
  'user1': [{message:'hello', username:'user1'}, {message:'data', username:'user1'} ],
  'user2': [{message:'sample', username:'user2'}, {message:'here', username:'user2'} ],
];

chat.[val.username] is not valid syntax, aren't you getting a syntax error for that? Is it actually chat[val.username]? — Barmar
– Barmar, Commented Sep 11, 2014 at 6:14
Why don't you put the init of 'chat' as first thing into the reorder function? — Kai Mattern
– Kai Mattern, Commented Sep 11, 2014 at 6:17
@Barmar yes sorry, I edited my post. assuming you have declared var data2 outside the function — loki9
– loki9, Commented Sep 11, 2014 at 6:17

elclanrs · Accepted Answer · 2014-09-11 06:19:03Z

1

You can do this easily with reduce:

var data2 = data.reduce(function(acc, x) {
  acc[x.username] = (acc[x.username] || []).concat(x)
  return acc
},{})
/*^
{ user1: 
   [ { message: 'hello', username: 'user1' },
     { message: 'data', username: 'user1' } ],
  user2: 
   [ { message: 'sample', username: 'user2' },
     { message: 'here', username: 'user2' } ] }
*/

answered Sep 11, 2014 at 6:19

elclanrs

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1 Comment

loki9 Over a year ago

COOL! I didn't know there's a function for this!! thanks! man. how did it do that?!

Barmar · Accepted Answer · 2014-09-11 06:24:35Z

0

The problem is that you made chat an array. When you look at an array in the console, it only displays the numeric indexes, not the named properties; you have to use console.log(chat) to see the named properties.

Since you want this to be an object with named properties, you should declare it as an object, not an array:

var chat = {};

answered Sep 11, 2014 at 6:24

Barmar

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Comments

user663031 · Accepted Answer · 2014-09-11 07:29:22Z

0

Use Underscore's _.groupBy:

_.groupBy(data, 'username')

answered Sep 11, 2014 at 7:29

user663031

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