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
– Mike Brant, Commented Jun 29, 2015 at 14:37
"but errors"?? You should share your experience of these errors. — spender
– spender, Commented Jun 29, 2015 at 14:38
You're replacing new_item on every single iteration of your loop. — Cerbrus
– Cerbrus, Commented Jun 29, 2015 at 14:40
Take a look at this question, stackoverflow.com/questions/920930/… — bob0the0mighty
– bob0the0mighty, Commented Jun 29, 2015 at 14:43

Explosion Pills · Accepted Answer · 2015-06-29 14:39:55Z

2

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.

answered Jun 29, 2015 at 14:39

Explosion Pills

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Comments

Yavor Ivanov · Accepted Answer · 2015-06-29 14:41:09Z

1

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

answered Jun 29, 2015 at 14:41

Yavor Ivanov

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Andy E · Accepted Answer · 2015-06-29 15:27:19Z

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, 2015 at 15:27

Andy E

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