const BigBag = {
    _weight: 0,
    _capacity: 0,
    _item : [],
    set capacity (cap)  {
        this._capacity = cap;
    } ,

    get items () {
        return [...this._item];
    },

    insertItem (item, weight) {
        this._item.push( {item, weight})
    }
};


BigBag.capacity = 30;
BigBag.insertItem("Blabla", 10);

let items = BigBag.items;
console.log(items);