[j0hnik]

https://developer.mozilla.org/ru/doc...cts/Array/push

var arr = [];

class Art {
    constructor() {
    }
    add(date, amount, currency, product) { 
        this.date = date;
        this.amount = amount;
        this.currency = currency;
        this.product = product;
        arr.push([date, amount, currency, product]);
    }
    list() {
        return arr;
        console.log(arr);
    }
    clear(date) {
        arr.splice(1,1);
        console.log(this.list());
    }
    total() {
        return this.amount + this.currency;
    }
}


const art = new Art();

art.add('2017-04-25', 2, 'USD', 'Jogurt');
art.add('2017-03-13', 5, 'EUR', 'Milk');

console.log(art.list());

console.log(art.total());