[Nexus]

Попробуйте так:

$.getJSON("https://www.cbr-xml-daily.ru/daily_json.js", function(data) {
    const currencies = ['USD', 'EUR'];

    const courses = currencies.reduce((result, currencyName) => {
        const currencyData = data.Valute[currency];

        const isIncrease = currencyData.Value >= currencyData.Previous;
        const html = `<b style="color:#${isIncrease?'00ff00':'ff0000'};"> в–${isIncrease?'I':'J'}</b>`;

        result[currencyName.toLowerCase()] =
            `${currencyName} ЦБ&nbsp;&nbsp;${currencyData.Value.toFixed(1)}${html}`;


        return result;
    }, {});


    Object.keys(courses).forEach(containerId => {
        $('#' + containerId).html(courses[containerId]);
    });
});