[рони]

c4udok,

document.addEventListener("DOMContentLoaded", function() {
    let db = [{
            ISO4217: '$',
            multiply: 1
        },
        {
            ISO4217: 'RUB',
            multiply: 70.5
        },
        {
            ISO4217: 'UAH',
            multiply: 27
        }
    ];
    document.addEventListener('change', function({target}) {
        if(target.closest('#valuta, [name="nameRadio"]')) {
        let option = db[document.querySelector('#valuta').selectedIndex];
        rebuildPrices(option);
        }

    });

    function rebuildPrices({ISO4217, multiply}) {
        const val = document.querySelector('[name="nameRadio"]:checked').value || 1;
        document.querySelector('#rezultatRadio').innerHTML = val;
        [...document.querySelectorAll('[data-cost]')].forEach(el => {
            const num = el.dataset.cost,
                  span = el.querySelector('span');
            span.innerHTML = `${(num * multiply * val).toFixed(2)} ${ISO4217}`;
        })
    }
    rebuildPrices(db[0])
});