How can i read this object property ? Moltin API

I'm using Moltin API, what i need is take the category id from the current product.

what could be simple like this:

product.category.id

but, what i get is....

product.category.data.1353881339752874661.id

how can i take this object property dynamically?

below is a print from my browser console:

Yo can do that by iterating the Keys of product.category.data object.

for (var key in product.category.data){
 // use key to refer to each key of the Object.
}

Another option could be, getting the different ids using the Objet.keys() method.