how to reformat this javascript array?

Question

i have variable like this

var item = [
            {'id': '1', 'quantity': '100'},
            {'id': '2', 'quantity': '200'}
        ];

but i need to change like this format

var new_item = {
            '1': {'quantity': '100'},
            '2': {'quantity': '200'}
        };

i do loop like this, but errors

for(i=0; i<item.length; i++){
            new_item = {
                item[i].id: {'quantity': item[i].quantity}
            };
        }

how can i change this format T__T

UPDATE FIX:

oh yes i just need to change like this

for(i=0; i<item.length; i++){
            new_item[item[i].id] = {'quantity': item[i].quantity};
        }

that work, sorry for my damn question, i think i'm too sleepy, thx guys ^_^

That is not JSON (which is a serialization format). That is simply a javascript array of objects. — Mike Brant, Jun 29 '15 at 14:37
"but errors"?? You should share your experience of these errors. — spender, Jun 29 '15 at 14:38
You're replacing `new_item` on every single iteration of your loop. — Cerbrus, Jun 29 '15 at 14:40
Take a look at this question, https://stackoverflow.com/questions/920930/how-to-create-json-by-javascript-for-loop — bob0the0mighty, Jun 29 '15 at 14:43

score 2 · Accepted Answer · answered Jun 29 '15 at 14:39

You need to use bracket notation to set derived keys. Initialize new_item = {} first.

new_item[item[i].id] = {quantity: item[i].quantity}

Note that if you were using ECMAScript6 you can use computed property names in object initializers like so;

new_item = {
    [item[i].id]: {quantity: item[i].quantity}
}

However, this overwrites new_item each time so it would ultimately only have the last value of the array.

score 1 · Answer 2 · answered Jun 29 '15 at 14:41

1

for(i=0; i<item.length; i++){
    new_item[item[i].id] = {'quantity': item[i].quantity};
}

answered Jun 29 '15 at 14:41

Yavor Ivanov

score 1 · Answer 3 · answered Jun 29 '15 at 15:27

1

You can do this using reduce if you don't need IE 8 support:

var newItem = item.reduce(function (o, c) {
    o[c.id] = c.quantity;
    return o;
}, {});

answered Jun 29 '15 at 15:27

Andy E

3 Answers3